LIBRARY OF CONGRESS. 



— ■ V Vl5 

UNITED STATES OF AMERICA. 



II 



MODERN EXAMINATIONS 

OF 

STEAM ENGINEERS 



OR 



Practical Theory Explained and Illustrated. 

WKITTEN rOR ENGINEEES BY AN El^GINEEE. 



CO.nPRlSING rULL AND CO/nPLETE ANSWERS TO 300 QUES- 
TIONS EOR THE USE OE ENGINEERS AND ElRE/nEN, WHEN 
PREPARING TO AAICE APPLICATION TOR EXAMIN- 
ATION ro:^ U. S. GOVERNMENT AND STATE 
LICENSE: AND TOR THE INFORMATION 
or ENGINE BUILDERS. BOILER 
MAKERS, MACHINISTS, ETC. 






BY 



W. H. WAKEMAN, 



INSTRUCTOR IN STEAM ENGINEERING AT THE BOARDMAN 
/MANUAL TRAINING HIGH SCHOOL. NEW HAVEN, CONN. 
ASSOCIATE EDITOR "MACHINERY," NEW YORK. N. 
^■. INSTRUCTOR ELM CITY STATIONARY EN- 
GINEERS' ASSOCIATION, N.A.S. E., NO. 
10, OP CONN.. AND AUTHOR OE 
MANY EDITORIALS EOR 
MECHANICAL PUBLI- 
CATIONS. 




FIRST EDITION. 
BRIDGEPORT, CONN. XC^mu^s. 

AMERICAN INDUSTRIAL PUBLISHING CO 

1895. ^ ^ X ^ 



h 



-tHi 






COPYRIGHTED BY 

W. H. WAKEMAN. 

1895. 
All rig-hts reserved. 




PRESS OF 

THE UNION PUBLISHING CO., 

BRIDGEPORT, CONN. 



PRE FA CE, 



The author takes pleasure in presenting- to the 
steam engineers of America, a work treating* in a 
plain, practical way of a g-reat variety of subjects 
pertaining- to the engine and boiler rooms, con- 
taining valuable and important information for 
those who aspire to become competent engineers, 
and something more than starters and stoppers. 

The authorities quoted are reliable and up to 
date, and the formulas and rules given are fully 
explained, thus enabling all to understand and 
apply them. 

The Manufacturers Gazette, of Boston, Mass., 
originally published this work, one part appear- 
ing in each weekly issue for an entire year, and as 
it was very favorably received by steam and me- 
chanical engineers, boiler makers, machinists, 
draughtsmen, etc., it is now published in book 
form for the convenience of those who wish to 
use it in daily practice. 

That the benefits derived from it by the craft 
may be commeasurate with the labor of preparing 
this volume, is the sincere wish of 

THE AUTHOR. 
June 22nd, 1895. 



DEDICA TION. 



To those true friends among- the eng-ineers of 
the United States of America who have ever been 
ready to g-ive encourag^ement and support, to the 
efforts of the author for the elevation of the po- 
sition of the practical eng-ineer, this book is re- 
spectfully dedicated. 

W. H. Wakeman. 

New Haven, Conn., U. S. A. 



CONTENTS. 



CHAPTER I. 

Introduction. .A Right and a Wrong way to Prepare 
for Examination .." Book Engineers are not Always 
Despised.". .Theory will do Practice no Harm.. The 
Ceaseless Routine of the Engine Room is Rendered 
Less Monotonous by Devoting a Portion of the Time to 
Study. 

CHAPTER H. 

General Outline of Subjects that Should be Familiar to 
Applicants for Other than First Class Licenses. .They 
Should be able to give Details of the Plant that they 
are to Run, and be Ready to Tell what Course to Pur- 
sue in Case of Accident, and also be Ready to Explain 
the Construction and Operation of the Slide Valve. 

CHAPTER HL 

Much is Usually Expected From the Applicants for First 
Class Licenses. .They Should Thoroughly Understand 
the Meaning of the Terms "Lap" and "Lead," and 
Know what is Meant by Clearance, Compression, 
Cushion, Cut-off, and Understand How to Set all 
Kinds of Valves. .They Should also Understand How 
to Properly Reverse an Engine. 

CHAPTER IV. 

All Rules Given for Reversing an Engine are not Cor- 
rect. .Travel of the Crank and Wrist Pin Compared. . 
How to Find the Throw of an Eccentric . .The Effect 
of Reducing the Diameter of an Eccentric. .The Proper 
Size of Steam and Exhaust Pipes. 



» CONTENTS. 

CHAPTER V. 

The Proper Size of Steam and Exhaust Ports. .Diameter 
of Crank Shaft. .Size of Crank and Wrist Pins. .Diam- 
eter of Connecting Rods and Piston Rods. .Length and 
Diameter of Main Bearings. .The Value of a Counter- 
bore. 

CHAPTER VI. 

Condensing and Non-condensing Engines. .Absolute 
Back Pressures. .Difference Between an Automatic 
and a Throttling Engine. .Compound, Triple and 
Quadruple Expansion Engines. .Good and Bad Quali- 
ties of these Types. What will the Engine of the 
Future be ? 

CHAPTER VH. 

What is Meant by the Horse Power of an Engine ?. .How 
to Determine the Power of any Engine. .One and Eight 
Horse Power. .Diameter of Cylinder, Length of Stroke, 
Speed, and Mean Effective Pressure Should be Stated. 

CHAPTER VHL 

How to Ascertain the Area of a Piston. .Deducting One- 
Half the Area of the Piston Rod. .How to Determine 
the Speed, or the Diameter of the Piston When all 
Other Data is Given.. Short Rule for Finding the 
Square Root of Certain Numbers. 

CHAPTER IX. 

Explanation of the Rule for Extracting the Square Root 
of any Number. .To Determine the Necessary Mean 
Effective Pressure, When all Other Data is given. .How 
to Ascertain the Horse Power Constant of any Engine, 
and Showing the Value of the same. .Increasing the 



CONTENTS. S> 

Power of an Engine. . Limit of the Size of a new Cy- 
linder. . Boiler Capacity for the Engine Under the 
new Conditions. .Shall We add a Condenser ?. .Best 
Remedy for an overloaded engine. 

CHAPTER X. 

Determining the Speed of an Engine Before Steam is Ad- 
mitted to It. .Revolutions of the Governor. .Does the 
Engine Run the Governor, or Vice Versa. .To Calcu- 
late the Speed of the Governor when all other Data is 
furnished. .The Size of Pulleys and Speed of Shafting 
..Why do We Use the Diameter of Pulleys Instead of 
the Circumference ? 

CHAPTER XI. 

The Ratio of Expansion. .Rule for Determining the 
Mean Effective Pressure Under Certain Stated Condi- 
tions. .Hyperbolic Logarithms and the Rule for Find- 
ing them from Common Logarithms. .Why the Num- 
ber lo is Used. .To Determine the Actual Point of Cut 
Off. .What is a Crank ?. .What is Meant by the Valve 
Gear of an Engine ? 

CHAPTER XII. 

What is a Fly Wheel ?. .How does it assist in Regulating 
the Speed of an Engine ?. .Rule to Determine the 
Weight of Rim.. What Does This Rule Recognize? 
.. Effect of a Heavy Rim on the Strength of the Wheel 
. .Rule for the AVeight of Entire Wheel . .Safe Limit of 
the Speed of Fly Wheels. .All Fly Wheels Should.be 
Carefully Balanced. .Bolting Split Wheels Together. 

CHAPTER XIII. 
Adding a Condenser to a Non-Condensing Engine.. 
Does it Increase the Mean Effective Pressure ?. .Re- 



10 CONTENTS. 

ducing Boiler Pressure and Maintaining Mean Effective 
Pressure. .Reduction of Absolute Back Pressure. .Sav- 
ing Steam by use of Condenser. .Increasing the Con- 
densation on Account of Low Terminal Pressure. .De- 
termining the Point of Cut Off when the Mean Effec- 
tive and Initial Pressures are Given. 

CHAPTER XIV. 

From the Engine to the Boiler. .The Source of Power 
Must be Understood. .Reducing Common to Decimal 
Fractions. .Safe Working Pressure of a Steam Boiler. . 
Thickness of Plate and Strength of Joint Must be 
Taken Into Account. .Tensile Strength and Factor of 
Safety. .Other Rules for Safe Working Pressure.. 
Coefficient of Safety. .All Safe Pressure Rules are not 
Practical. .Four Rules Compared. .Aggregate Strain 
Caused by the Steam Pressure. 

CHAPTER XV. 

Boiler Seams. .The Weakest Part Must be Taken for the 
Calculation. .Pitch of the Rivets. .Strength of net 
Section of Plate. .Strength of the Rivets. .Comparing 
Strength of Joint and of Solid Plate. .Double Welt 
Butt Joints. 

CHAPTER XVI. 

Bracing Flat Boiler Heads. .Bracing from Head to Head 
and from Head to Shell. .Safe Load for Braces. .Ag- 
gregate Pressure on a Flat Head.. Braces Should be 
made Without Welds. .They Should not be Riveted to 
the Fire Sheets.. The use of Tee Irons. .Strength of 
Seams with Drilled and with Punched Holes. .Effect of 
Flanging the Boiler Heads 



CONTENTS. 11 

CHAPTER XVII. 

Heating Surface Necessary for a Horse Power. .Square 
Inches on the Engine Cylinder and Square Feet on the 
Boiler Shell. .Hot and Cold Feed Water. .What Consti- 
tutes a Horse Power ?. .Determining the Heating Sur- 
face of a Boiler, .The Shell and the Heads. .Water 
Space of a Boiler. .The Steam Space Must Include the 

. Dome. .Foaming and Priming. .Removing Some of 
the Tubes and Putting in a Dry Pipe. .Value of a Sep- 
arator 

CHAPTER XVIII. 

Proper Size of Safety Valve for Any Boiler. .The Grate 
Surface and the Heating Surface. .English and French 
Rules.. U. S. Rule the Best. .Area of Opening. .Dif- 
ference Between Flat and Bevelled Seats. 

CHAPTER XIX. 

Areas of the Openings of Safety Valves Further Consid- 
ered. .Examples Illustrating the Same. . Proper Size of 
Pump for a Steam Plant. .Hot and Cold Water Pumps 
. .Water Needed in Winter and Summer. .Calculating 
the Capacity of a Pump. .How Water is Raised. .Limit 
of the Height to which a Pump can Lift Water, .Prac- 
tical Limit to the Same. 

CHAPTER XX. 

Advantage of Heating Feed Water. .Heating it by Ex- 
haust Steam. .Rule for Determining the Percentage of 
Fuel Saved. .Illustration of the Same.. Forced and 
Natural Draft. .Fan Blower and Steam Jet. .Efficiency 
of the System. .Designing Chimneys. .Rule for the Size 
of Chimney for any Plant. 



12 CONTENTS. 

CHAPTER XXI. 

A General Knowledge of the Steam Engine Indicator is 
Necessary. .Description of the Instrument. .Slight De- 
fects Produce Serious Consequences. .The Admission 
and the Steam Lines. .The Expansion and the Counter- 
pressure Lines. .The Atmospheric and the Vacuum 
Lines. .Height and Weight of the Atmosphere. .The 
Forward Pressure is not the Mean Effective Pressure. . 
Three Ways of Ascertaining the Mean Effective Pres- 
sure. 

CHAPTER XXII. 

Rules for Locating the Theoretical Expansion Line.. 
Proving the Rule for Determining the Mean Effective 
Pressure. .Calculating the Water Consumption . .A 
Pound of Water Makes a Pound of Steam. 

CHAPTER XXIII. 

Explaining Rules for Calculating Water Consumption.. 
Pressure at the Point of Release. .Weight of a Cubic 
Foot of Steam. .Cubical Contents of the Cylinder. .The 
Horse Power Developed. .The Principle Involved 
Should be Understood . .Every Point Should be Taken 
Into Consideration. 

CHAPTER XXIV. 

Formula Used by the Massachusetts School of Technol- 
ogy . .Illustration of Its Application . .How Different 
Values were Obtained . .Small Differences will not 
Prevent the Applicant From Receiving a License. 

CHAPTER XXV. 

Comparison of Four Rules for Calculating Water Con- 



CONTENTS. 13 

sumption. .A Rule which is Short but Requires a Table 
to Make it Complete. 

CHAPTER XXVI. 

Conclusion of the Subject of Water Consumption . .The 
Rate Maybe Changed Without Changing the Engine. . 
Light and Heavy Loads. .Reduction of Speed and De- 
creased Output of Machinery. 

CHAPTER XXVH. 

Conclusions Should not be Hastily Arrived At. .Initial 
Cylinder Condensation and Re-evaporation. .Exact 
Clearance not Always Known. .Causes for Improperly 
Located Expansion Lines. .Exposed Cylinders Should 
be well Covered with Some Non-Conductor. .A Badly 
Set Steam Valve and the Cause of it. .Counter Pressure 
and Compression Lines. .Concerning the Proper 
Amount of Compression. 

CHAPTER XXVIII. 

Direct Steam and Expansion .. Do we Save Fuel by 
Using Steam Expansively ?. . " Power Developed " and 
"Work Done".. When Absolute Pressures Should be 
LTsed . .An Easy Way to Prove a rule. .The Most Eco- 
nomical Pressure to Carry. .A High Boiler Pressure, 
Economical Under Certain Condition 

CHAPTER XXIX. 

Effect of Lowering the Boiler Pressure.. An Engine 
Should be Properly Proportioned For Its Work. .Prin- 
ciple on which a Compound Engine Operates. .Cylin- 
der Condensation an Unknown Quantity. .Why Piston 
Rods of Cross Compound Engines may be the same 
Diameter. 



14 CONTENTS. 

CHAPTER XXX. 

Amount of Water Needed for a Surface Condenser. .Effect 
of Condenser on Temperature of Feed Water. .Explan- 
ation of Rule for Water Needed. .How to Calculate the 
Power Developed by a Compound Engine. .Water Rate 
for a Compound Engine. .Adding a Low Pressure 
Cylinder to a Simple Engine. 

CHAPTER XXXI. 

Water for a Jet Condenser. .Volume of Water in Steam 
. .Density and Weight are not the Same. .How to Cal- 
culate the Density From the Weight and Vice Versa. 

CHAPTER XXXH. 

Size of Injection Pipe. .Explanation of the Rule for De- 
termining it. .Water Above and Below the Condenser. . 
Great Care is Necessary when Indicating an Engine. . 
The Horse Should Always be put Before the Cart. 

CHAPTER XXXIII. 

Steam Heating for Buildings. .Three Systems in Use.. 
Explanation of the Difference Between Them. .Heating 
and Ventilating with the Same Apparatus. .Heating in 
Winter and Cooling in Summer with the Same Ma- 
chinery. 

CHAPTER XXXIV. 

Four Different Ways of Piping the Direct Radiation 
System for Steam Heating. .Cost and Efficiency Com- 
pared . .Angle Valves are Recommended. .Water Ham- 
mer. .Admitting Steam to the System. .How to Locate 
the Position of a Globe Valve. .Asbestos Wicking for 
Packing Valve Stems. 



CONTENTS. 15 

CHAPTER XXXV. 

Radiating Surface Necessary to Heat a Room .. Heating 
and Cooling Surface. . Effect of Glass Surface.. Re- 
ducing all Wall Surface to a Common Standard. 

CHAPTER XXXVI. 

Difference in Temperatures to be Considered when Esti- 
mating the Radiating Surface for a Room. .Allowances 
to be Made.. Area of Main Steam Pipe. .Two Rules 
for this Purpose. .Heating Surface of the Boiler.. 
Efficiency of Direct Heating Surface, and Tube or 
Flue Surface. 

CHAPTER XXXVn. 
The Value of Exhaust Steam for Heating Purposes. .How 
to Calculate the Cost of the Same. .Heavy Back Pres- 
sure not a Necessity. .How to Arrange the Piping for 
Good Results. .A Trap is Advisable. .Live Steam May 
be used in the Same System. 

CHAPTER XXXVHI. 

Strength of Shafting. .Conditions to be Considered.. 
Diameter of Wrought Iron Shafting to Transmit a 
Given Horse Power. . Example Illustrating the Rule . . 
Power That a Shaft Will Safely Transmit. .Diameter 
and Power of Steel Shafting. .Cast Iron Shafting.. 
Formula for Crank Shafts for Compound Engines. 

CHAPTER XXXIX. 

Diversity of Opinion Concerning the Power of Belting. . 
A Good Formula. .Half Angle of Contact. .The Size of 
Pulley Is a Factor. .Speed of Belting. .Safe Load.. 
Formula for Breadth of Belt for a Given Horse Power 
. .Strength of Double and Single Belts. .Endless Belts 
Are Recommended. 



16 CONTENTS. 

CHAPTER XL. 

Why Do Steam Boilers Explode?. .Superheated Water 
Theory.. Heat Generated When Fires Are Banked.. 
Effect of Opening the Throttling Valve to Start the 
Engine. .When Steam Boilers Explode. .Accumulation 
of Electricity. .Is Lightning a Factor?. .Pumping in 
Cold Water. .Effect of Heating Plates Red Hot. 

CHAPTER XLL 

More About Steam Boiler Explosions. .Is Low Water the 
Only Cause?.. What Becomes of the Water When a 
Boiler Explodes?. .Effect of a Ruptured Plate. .Other 
Theories. .The Real Cause for Explosions. .It is Better 
to Know Before Than After. .An Evaporative Test 
Does Not Always Demonstrate the Value of a Boiler. 

CHAPTER XLII. 

Steam Boiler Explosions Still Further Considered .. Bor- 
ing Holes in the Shell. .Improperly arranged Settings. . 
Insufficient Bracing. .Poorly Constructed Braces.. 
Boilers Wear Out. .Illustrating the Work Done by a 
Boiler. .Circulation of the Water. .Effect of Unequal 
Contraction. ."Nobody to Blame." 

CHAPTER XLIII. 

Necessity for Covering Steam Pipes. .Best Kind to L^se. . 
Air and Coal. .Process of Combustion. .Air Necessary 
to Burn a Pound of Coal. .Weight and Volume of Air. 

CHAPTER XLIV. 

The Bursting Pressure of a Boiler. .Thickness of Boiler 
Plate. .Strength of Shell Plates. .Explanation of Rules 
Given .. Elastic Limit of Boiler Heads.. Safe Working 



CONTENTS. 17 

Pressure of a Head Without Braces. .Tensile Strength 
and Elastic Limit. .Tons and Pounds. .American and 
English Practice. 

CHAPTER XLV. 

Boiler Heads. .Cast Iron Dome Heads. .Deflection Within 
the Elastic Limit. .Improving the Qualit}^ of Cast Iron 
..Spherical or Bulged Boiler Heads . .Increasing the 
Safe Working Pressure .. Head and Shell of the Same 
Thickness. .Tensile Strength and Elastic Limit Must not 
be Called the Same Thing. Strength of a Concave 
Head. .Modifying Conditions. 

CHAPTER XLVI. 

Wrought Iron Heads for Boilers. .Steel and Cast Iron 
Heads. .Rules to Determine Elastic Limit of Heads 
Made of Different Materials. .Clear Distance Apart of 
Braces. .Rules to Determine Thickness of Plate, 
Strength of Plate, and Pressure That May Safely be 
Carried.. Are the Braces Strong Enough to Carry 
Their Load . .Estimating the Strength of Threaded 
Stay Bolts 

CHAPTER XLVII. 

Bracing Boiler Heads. .Details of the Problem. .Locating 
the Braces. .Illustrating the Rule.. The Surface to be 
Braced and the Pressure to be Carried. 

CHAPTER XLVIII. 

Segments of Circles. .What is a Segment ?. .The Arc and 
the Chord. .Illustrating the Rule . .Segments May be 
Larger or Smaller Than a Semi-circle. .Measuring the 
Length of Curved Lines. .Square Inches Supported 
by a Boiler Brace. .Number of Braces Needed.. Re- 
ducing tne Number of Braces. 



18 CONTENTS. 

CHAPTER XLIX. 

Strength of Tee Irons. .The Web and the Flange. .Ten- 
sion and Compression. .The Neutral Axis. .The Flange 
in Tension.. The Datum Line.. The Axis a Fixed 
Point. .Some Parts of the Beam More Effective Than 
Others. 

CHAPTER L. 

Compressive and Tensile Strength of Tee Irons. .Lo- 
cating the Center of the Tensile Stress. .The Centre of 
Compressive Resistance. .The Total Compressive Re- 
sistance. .No Formula Given. .A General Rule. 

CHAPTER LI. 

Calculating the Load on Tee Irons. .Distributing the 
Braces. .The Span or Distance Between Supports.. 
Braces May be Needed Below the Tubes. .Always be on 
the Safe Side. 

CHAPTER LII. 

Collapsing Pressure of Tubes. .Application of the Rule. . 
A Large Factor of Safety. .The Length of the Tube 
Must be Considered. .Safe Working Pressure of Tubes 
and Lap Welded Flues. .Comparison of Rules.. Ex- 
amples Illustrating the Same, .Rule to Determine 
Thickness of Flues. .All Parts of the Boiler will Stand 
the Designated Pressure. 

CHAPTER LIII. 

Conclusion of the Whole Matter. .Time Required to 
Make an Engineer. .Sometimes Ignorant Engineers 
Claim to Know it All. .A Key for the Storehouse. .Re- 
liable Rules Based on Common Sense. 



MODERN EXAMINATIONS 

OF 

STEAM ENGINEERS 



BY 
W. H. WAKEMAN. 



CHAPTER I. 



INTRODUCTION. — THEORY WILL DO PRACTICE NO 

HARM. 

This book is intended to g-ive information to 
those eng'ineers who wish to qualify themselves to 
pass examinations and take out licenses to run 
stationary eng^ines in those localities where such 
licenses are required. To many engineers, who 
are interested in the business by which they g^ain 
a livelihood, but who are employed in localities 
where no licenses are required, the idea of g-oing 
before a board of examiners, passing- an exam- 
ination and receiving aleg-al document with a larg-e 
seal thereon affixed, stating- that the owner is quali- 
fied to care for and manage steam eng-ines and 
boilers, is a very fascinating* one, and the desire 
for knowledg-e which will enable them to pass an 
exammination almost universal. 

The writer has been amused in noting* the way 
in which some of them expect to g-et the necessary 



20 MODERN EXAMINATIONS 

information, for while they have a fair situation, 
and no license needed, they are content to merely 
wish that they possessed the qualifications called 
for in other places, and are too "shiftless" to 
study up the points, but when they secure a situa- 
tion where their knowledge of steam eng-ineering- 
is to be put to a test they are very active. 
They will come to you full of zeal for the new 
conditions under which they are to work, state 
that they want to get posted, and g-ive you the 
idea that they expect you to attach a hose to their 
brain, in some mysterious manner, and start up a 
pump, and pump them chock full of information 
in about half an hour. Some of them expect to 
get a list of questions that the inspector will ask 
them, together with the answers to the same, and 
having secured these, and learned them in the 
same way that a parrot or jackdaw learns to 
swear, that they can then go up to the pompous 
looking official who presides over the inspectors' 
department, and compel him to give one of the 
coveted prizes. 

Reader, did you ever attend school in your boy- 
hood days, where long lessons in spelling were 
allotted you, and becoming desperate on account 
of repeated failures, adopted a plan which you 
thought would enable you to go home when the 
other boys did? This plan was to note 5^our po- 
sition in the class (near the foot), and select the 
words which it would naturally be your turn to 
spell, and learn them thoroughly. But do you 
remember how you were seized with consterna- 
tion when you discovered that the teacher began 
at the other end of the class to give out the 
words, thus putting those to you that you had 
not even attempted to learn to spell? If you have 
been through this experience, you were probably 



OF STEAM ENGINEERS. 21 

impressed with the idea that the only sure way 
was to learn the whole lesson. And so it will be 
with men who expect to learn a few questions and 
answers, and so get a first-class license, for they 
will find that the answers that they did not learn 
are just the ones that they will be required to 
g-ive, and consequently the only sure way, if a 
first-class license is needed, is to learn the whole 
lesson. The whole lesson did we say? That 
means a great deal, for probably none of us have 
accomplished that feat, and in this respect the 
comparison does not hold good, but at the same 
time, if all engineers who carefully read the whole 
of this series of articles will make themselves 
familiar with all the subjects treated of, together 
with those that may be suggested by them, they 
will not fear to go before any board of examiners, 
and submit themselves to a fair test as to their 
knowledge of engines, boilers, etc. 

Occasionally we meet a man who claims that he 
knows how to run an engine, but that he cannot 
tell others how it is done, but such an excuse ap- 
pears to be very unsatisfactory, for while we may 
not be able to express ourselves in as correct 
language as others do, still if we really know how 
these things are done, we can usually find some 
way to tell it to others. The fact is that there 
are many good men in charge of steam plants who 
were formerly firemen, and through faithfulness 
and sobriety have been promoted, and get along 
after a fashion, without really knowing anything 
of the theoretical part of the business. Such 
men can keep their plants clean, practice economy 
in the use of supplies, and are devoted to the in- 
terests of their employers, but at the same time 
just as soon as any question comes up which re- 
quires a little *' head-work" to settle, they are 



22 MODERN EXAMINATIONS 

ever ready to call upon others to help them out of 
their troubles, although at other times they affect 
to despise them, on account of being what they 
are pleased to term "book engineers" or *' paper 
engineers." Well, we are of the opinion that the 
well-posted ones can stand it if the others can, for 
it is a well-known fact that these men speak dis- 
paragingly of their fellows to divert attention 
from their own defects. 

I trust none of my readers are ready to admit 
that they are in this class, but if there are any 
such, allow me to ask a few questions. As you 
now claim to understand the practical part of 
your business, do you think that it would detract 
from the knowledge already possessed if you 
should acquaint yourself with the theoretical part 
of your occupation? As you now know that it is 
well to have your safety valve weight set so that 
the valve will open when the gage indicates 80 
pounds pressure, and find it a good plan to lift 
the valve from its seat once every day, would it do 
you any harm if you knew how to determine the 
area of said valve, and also how to calculate the 
pressure at which it should lift, all necessary data 
being given, and then compare it with the results 
obtained in practice? Are you aware that such 
knowledge will tend to lighten the work in the fire 
room, and relieve the monotony of the ceaseless 
routine of the engine room? We beg pardon for 
this digression, and will return to our subject. 
While a list of direct questions are necessary in 
examining a candidate, still it is not the intention 
of the writer to give a catechism at this time, but 
the subjects will be treated in a more general way, 
believing it to be the best plan. 



OF STEAM ENGINEERS. 23 



CHAPTER II. 

GENERAL OUTLINE OF SUBJECTS THAT SHOULD 

BE FAMILIAR TO APPLICANTS FOR OTHER 

THAN FIRST CLASS LICENSES. 

Applicants for a license other than first class 
are expected to have a general knowledge of the 
plant which they are to have charge of, for in 
these cases the license is given to run a certain 
plant, and will not qualify a man to take charge of 
any plant that he may be hired to run. A misun- 
derstanding concerning this point has caused 
some rather embarrassing mistakes, for if a man 
conceives the idea that it would be a help to him 
in securing employment, provided he has a license 
to show, and, acting on the happy thought, ap- 
plies for one on general principles, about the first 
question that he will be asked will prove to be a 
hard one to reply to, for he will be asked to state 
where he is to be employed, and as this is the 
very question that is puzzling him in his own 
mind, he can scarcely be expected to give an 
intelligent reph^ But having secured a situation, 
his next care should be to get a good idea as to 
the details of his plant. He should know the 
diameter of the cylinder of his engine, the length 
of the stroke and the number of revolutions per 
minute. He should be able to state whether it is 
an automatic or an adjustable cut-oif, or one of 
the fixed, cut-off, throttling type; the size of the 
steam and exhaust pipes should be given, and a 



24 MODERN EXAMINATIONS 

general description of the whole eng-ine prepared, 
so that almost any question as to the size of any 
of the parts can be answered. The boiler or 
boilers should also receive attention, and a gen- 
eral description of them be prepared, including- 
their diameter and leng-th, the thickness of the 
material of which they are composed, and 
whether they are of iron or steel, the number 
and the diameter of the tubes or flues in them, 
the size of the furnaces and the kind of setting- 
adopted. The boiler feeders should not be over- 
looked, but the diameter of the water pistons or 
plung-ers g-iven and the length of their stroke. 
Whether an injector is provided or not, and, if 
so, is it of the liftitig- or the non-lifting- type, and 
its rated capacity should be known ; this to be 
determined by reading- the maker's catalog-ue, and 
an opinion g-iven as to whether the capacity of 
each of them, in cases where more than one boiler 
feeder is provided, is sufficient for the needs of 
the plant. 

It will do no harm for the candidate to review 
some ordinary questions concerning- his every- 
day practice in the eng-ine and boiler room, and as 
to what he would do in cases of emerg-ency. He 
should remember that his first duty on entering 
his boiler room in the morning is to ascertain 
where the water level in the boiler is, this always 
to precede the opening of the damper. It is not 
sufficient to know that there was three gages 
there the night before, and that, as the floor is 
not flooded, it demonstrates that it is still there, 
for there are several ways whereby it might have 
made its escape unnoticed. 

Probably there are few engineers who have not 
at one time or another found less water in the 
boiler than they anticipated, and although month 



OF STEAM ENGINEERS. 25 

after month slips away and the above-mentioned 
precaution seems entirely unnecessary, still it 
should never be neglected, for no one can tell 
when such neglect will cause serious damage to 
be done. This also should receive all due atten- 
tion before firing up a boiler after it has been 
cleaned. 

He may be asked what he would do in case that 
he accidentally allowed the water to get low while 
the engine is running, to which he should always 
reply that he would never allow such a thing to 
happen, and if it is sug'g-ested that even the best 
of engineers forget to attend to their duties at 
times, he should never admit that it is possible 
for him to forget so important a thing as that. 
If, however, the feed pipe should burst, thus 
allowing the water to escape faster than it can be 
replaced, he should run the pump to its full ca- 
pacity, and, provided he can open the furnace 
door without being scalded, he should cover the 
fire with fresh coal or damp ashes, for the writer 
believes that this is a much better plan than to 
attempt to draw it, as when a fire is disturbed, it 
gives out a very intense heat for a few minutes. 
Of course a pipe may burst in such a way as to fill 
the furnace with steam and scalding water, thus 
preventing' the fireman or engineer from banking 
it, but in that case it will be so deadened down 
that it will not be capable of injuring the boiler. 

The size of the safety valve should be noted, 
and an opinion formed as to whether it is large 
enough for the purpose intended or not, and it is 
well to bear in mind the fact that careful engi- 
neers try their safety valves at short intervals, in 
order to know that they are ready to open when 
needed. 

It is the dutv of an eng-ineer to bank his fire 



26 MODERN EXAMINATIONS 

and shut down the plant whenever he is convinced 
that the boiler has developed a weakness, caused 
by a blister, a fractured plate, or any of the other 
ag*encies which work to cause its destruction, 
when such weakness has advanced sufficiently to 
warrant it, and no consideration should cause him 
to continue to run with a high pressure, thus en- 
dang-ering* lives and property. 

The applicant should familiarize himself with 
the construction and operation of the slide valve, 
as it is quite possible that he may be shown a 
model and asked to set it properly, and if he 
should find that it is so made that it cannot be set 
so as to work properly, it would not be the first 
time that an eng-ineer has been so tested. 

These questions, as will be noted, are of a 
plain, practical nature, and every man who claims 
to be an eng^ineer should be able to readily answer 
them. 



OF STEAM ENGINEERS. 27 



CHAPTER III. 

DIRECTIONS TO THOSE WHO DESIRE A FIRST CLASS 

LICENSE. 

We now come to matters with which the candi- 
date for the honor of holding- a first-class license 
must be familiar, in order to be sure of passing* a 
satisfactory examination. But a small proportion 
of the licenses issued are for this class, because 
it is much easier to g^et one of the lower g^rade, 
which usually answers every purpose. 

The applicant is deterred from seeking- one by 
the fact that if he applies for one of a lower g-rade 
'^but which may be sufficient to answer his pur- 
pose), if he fails to pass the examination, he may 
try it ag-ain in a few days, but if he wants a first- 
class license, more will be naturally expected of 
him, and furthermore, if he cannot meet the re- 
quirements at his first trial, he may be oblig-ed to 
wait for three months before another trial will be 
g-ranted him, and in the meantime the situation 
that he wished to take will be secured by someone 
who has already passed the ordeal once, and con- 
sequently knows just what to expect. We would 
not be surprised if the examination were far less 
rig-id after a man has become well known to the 
inspector. 

It is perfectly natural in speaking- of the diif er- 
ent parts which constitute a steam plant to men- 
tion the eng-ine first, which rule will be followed 
here, and in enumerating- the parts of the eng-ine 



28 MODERN EXAMINATIONS 

we usually speak of the valve, and the machinery 
which operates it, first, and therefore we w^ould 
say that it is well for the applicant for a license to 
be thoroughly familiar with the principles here 
involved. There is a g-reat difference in the ways 
that men go about learning these things, for some 
of them appear to know no other way than to 
learn just how the several parts of a certain valve 
gear are to be adjusted in relation to each other, 
without understanding any of the principles 
which lie at the foundation of their operation. 
For instance, a man of this stamp will take charge 
of an engine, and among the first things that he 
will do will be to note the position of the eccen- 
tric on the crank shaft, the exact length of the ec- 
centric rod, and also of all of the other parts 
which are adjustable, and mark them in such a 
way that he will be able to replace them, should 
they ever become disarranged from any cause. 

Nearly all valves if properly made have lap, and 
if properly set they will have lead. This state- 
ment naturally suggests the question, what is lap? 
Let us suppose that the steam ports, or passages 
leading from the steam chest into the cylinder, 
are lyi inches wide, and when the slide valve is 
placed in the centre of its travel, the ends of it 
being made to cover up these ports, each end of it 
laps over the ports one quarter of an inch. That 
part which laps over the edge of the port towards 
the end of the valve is called outside lap, and that 
part which projects over the part toward the in- 
side or middle of the valve is called inside lap. 
These may not be good proportions but will do 
for illustration. 

The object in putting outside lap on a slide 
valve is to save steam by cutting off the supply 
from the boiler before the piston reaches the end 



OF STEAM ENGINEERS. 29 

of the stroke. The object soug-ht in putting- on 
inside lap is to close the exhaust port before the 
piston reaches the end of the return stroke, thus 
trapping- in some of the exhaust steam, (filling- the 
clearance), and raising- it to some considerable 
pressure, according- to the speed of the eng-ine 
and the judgment of the engineer. The effect 
is to make the eng-ine run quietly by bring-ing- 
the reciprocating- parts to rest, by the piston 
striking- ag-ainst a cushion, as it were, and also to 
save steam, for the portion of the wasteroom at 
the ends of the cylinder, which are thus filled 
with exhaust steam will not have to be filled with 
live steam.. 

The term lead, as applied to the working- of 
the steam eng-ine, is partially self-explanatory, 
for it means that the action of the valve in open- 
ing- must lead the action of the crank, taking- 
the dead centre as a starting- point; therefore if 
when the engine is on one of its centres the valve 
is open one-sixteenth of an inch, we say that 
it has one-sixteenth of an inch lead. Of course 
we mean that it must be open on the same end 
that the piston stands at, and care must be 
taken to see that the eccentric is set so that 
when the eng-ine is turned over in the direction 
that it is to run, the valve will continue to open, 
for it is possible to set it so that while it may g-ive 
the valve lead, still if the engine be turned over 
by hand, the valve will immediately close, and it is 
quite plain that it will not run even if steam is ad- 
mitted under those conditions. 

These principles apply to all valves of whatever 
form, size or description, and it makes no differ- 
ence whether they slide or rotate, lift or swing* to 
give opening of port. It is the same whether the 
steam is admitted over the end of the valve or 



30 MODERN EXAMINATIONS 

throug-h the middle of it. Whatever devices are 
used to turn the rotary motion of the crank shaft 
into the reciprocating motion of the valves does 
not affect them, and if engineers would be mas- 
ters of this idea it would save much hard work in 
studying" out how to set different valves. I do 
not mean to say that the eccentric would be in the 
same position on the shaft in all of the cases, for 
it would not, but the motion which opens the 
valve must precede the motion of the crank in 
every case. 

The connections between the crank shaft and 
the valves are made in different ways, and this will 
effect the position of the eccentric, for if a rocker 
arm is hung* at the bottom the eccentric must be 
put in a certain position to do its work properly, 
but if the rocker arm is changed and hung* in the 
middle, the eccentric will have to be put in an en- 
entirely different place, but the principle is the 
same, for the motion of the valve must be in ad- 
vance of the crank. To explain just what to do 
to set the valves of every kind of engine that is 
built would fill the pages of a large book, but if 
the eng-ineer tinderstands these principles, and 
then will carefully examine the engine that he is 
to adjust, he will soon see how the desired result 
is to be obtained. To reverse the engine, put it 
on the centre, and note the amount of lead that the 
valve has. Loosen the set screws, and turn the 
eccentric in the opposite direction from that in 
which it is intended that the engine shall run, un- 
til the valve has the same lead on the same end. 
Tighten the set screws, and the valve will be 
properly set, assuming that it was so before. 



OF STEAM ENGINEERS. 31 



CHAPTER IV. 

REVERSING AN ENGINE. — THROW OF THE ECCEN- 
TRIC. — STEAM AND EXHAUST PIPES. 

While on the subject of reversing" an eng'ine, it 
is proper to speak of rules given by others for 
this purpose, which do not ag"ree with the one 
just g'iven, for when the seeker after knowledge 
meets with two or more rules which do not agree, 
he is perplexed to know which one to believe. In 
two different books which give a so-called rule for 
doing this, one of which claims to be the only 
practical work published, I find the following 
instructions given: To reverse an engine, place 
it on the dead Centre, remove the steam chest 
cover, and note the amount of lead that the valve 
has. Loosen the set screws in the eccentric, and 
turn it in the opposite direction until the valve 
has the same lead on the opposite port; then the 
engine will run in the opposite direction. This 
is a mistake, for when an engine is to be started 
from the dead centre (or a little past the centre) it 
must take steam on the same end, regardless of 
the direction in which it is to run. If an engine 
is on one of its centres, and the valve admits 
steam to the opposite end of the cylinder from 
where the piston stands, how can it be started in 
either direction? In the first place, the whole 
volume of the cylinder must be filled with steam, 
which would constitute a very large clearance, to 
say the least, and then as the piston is already at 



32 MODERN EXAMINATIONS 

the end of the cylinder, how can it be forced any 
further in that direction? 

In turning* an eng-ine over from one centre to 
the other, it is interesting to note the difference 
in the travel of the crank pin and the wrist pin. 
There is before me, as I write the explanation of 
this problem, in a book written for the purpose 
of instructing* engineers in their duties: "A 
crank pin travels 1.1416 times further than the 
piston each revolution, or 0.5707 times further 
each stroke. For example, take an engine with a 
12-inch stroke, the piston travels 24 inches and 
the crank pin 37.6992 inches each revolution, or 
the piston travels 12 inches each stroke and the 
crank pin 13.6992 per single stroke of the pis- 
ton." This statement is a.bout as badly mixed up 
as it could be, for in the case of an engine with a 
12-inch stroke, the crank would be 6 inches long, 
and in making a revolution it would describe a 
circle whose diameter is 12 inches, and whose 
circumference is 37.6992 inches, and in making a 
single stroke or half a revolution, it will travel 
through just one-half of that distance. 

A few points about the eccentric may be of 
interest at this point. An eccentric is to all 
intents and purposes a crank and a crank pin. 
The distance from the centre of the eccentric to 
the centre of the hole bored in it for the shaft 
represents the length of the crank, and twice this 
distance gives us the stroke or throw of the 
eccentric, just the same as twice the length of the 
crank of an engine gives us the stroke of it. It is 
seldom convenient to take eccentric off from its 
shaft and measure these distances, therefore if it 
is desired to find the throw of it, while in posi- 
tion, measure the distance from the shaft to the 
edge of eccentric on the heavy side, and also on 



OF STEAM ENGINEERS. 33 

light side. Subtract one from the other and the 
remainder will be the throw of the eccentric. 

The diameter of the eccentric represents the 
diameter of the crank pin in this case, and 
although these proportions are very different 
from those used for the crank of an engine, still 
the principle is exactly the same. Sometimes 
engineers will ask this question: "If an eccen- 
tric is turned down, say from 10 inches in diam- 
eter to 9 inches, will it affect the travel of the 
valve?" We wish to ask a question. Suppose 
that we take an ordinary crank on an engine, and 
this crank projects beyond the crank pin to the 
extent of 3 inches. If we turn it off so that it ic: 
1 inch shorter than it was before, without dis- 
turbing the crank pin, will it affect the stroke of 
the engine? Of all those who read this chapter, 
probably not one will claim that it would, because 
as we have not changed the distance between the 
centre of the crank shaft and the centre of the 
crank pin, and this distance is what determines 
the stroke of the engine, so in putting the eccen- 
tric in a lathe and turning it down an inch, we 
have not changed the throw of it, because we have 
not changed the distance between the centre of 
the eccentric and the centre of the hole for the 
shaft. 

The applicant for a license should be able to 
calculate the size of steam pipe needed for any 
engine, and the old-time rule for this is that it 
should be one-quarter the diameter of the cylin- 
der. This may do very well for the slow piston 
speeds formerly used, but if that is sufficient for 
a speed of 300 feet per minute it does not 
necessarily follow that it will give the best re- 
sults for a speed of 600 feet. There is no 
unqualified rule that will apply to all cases, for 



34 MODERN EXAMINATIONS 

it is quite evident that an automatic engine will 
need a lar§*er steam pipe than a throttling- one of 
the same diameter will, for in the former case all 
the steam must be admitted before the cut-off 
valve closes, which may averag-e at quarter stroke, 
while in the latter case, with a cut-off fixed at 
three-quarter stroke, the pipe will be admitting- 
steam during- a space three times as long- as in the 
former to do the same work. 

Por an automatic engine running at a high 
piston speed, the pipe should be one-third diam- 
eter of the cylinder, but for a throttling one, if it 
is one-quarter the diameter of the cylinder, it will 
answer every purpose, for there is such a thing as 
having a pipe too large, causing greater loss from 
condensation. If the exhaust pipe is four-tenths 
of the diameter of the cylinder, it will be large 
enough to allow the steam to escape freely, with- 
out causing back pressure. A smaller pipe will 
answer every purpose if the engine has only a 
light load, but when this is increased to the full 
capacity of the machine, unless it is of ample size, 
it will cause unnecessary back pressure, and that 
at a time when it will be of the greatest disadvan- 
tage. 



OF STEAM ENGINEERS. 35 



CHAPTER V. 

STEAM AND EXHAUST PORTS. — DIMENSIONS OF DIF- 
FERENT PARTS OF AN ENGINE. 

The size of the steam and exhaust ports should 
receive due attention, and as the practice of the 
prominent eng"ine builders in desig'ning* them does 
not agree, it is rather puzzling- to any one who 
may seek to show that it will not do to depart 
from a rule that he may have adopted. One firm 
who manufacture a great many engines make the 
steam ports six per cent, of the area of the cylin- 
der and the exhaust ports 12 per cent, of it, while 
another high-grade engine builder makes them 8.7 
per cent, and 10 per cent, respectively. These 
are good samples of their class, and from the re- 
sults obtained from them it is safe to say that the 
steam ports should have 10 per cent, of the area 
of the cylinder, and the exhaust ports 12 per cent, 
of the same. 

The reasons for this conclusion are as follows : 
The engines having a steam port area of six per 
cent., do not maintain the initial pressure to the 
point of cut-off while running at a piston speed of 
500 feet, but the way that they exhaust the steam, 
even when very heavily loaded, is very satisfac- 
tory, while the engines with the 8.7 per cent, steam 
ports hold the steam line up remarkably well, al- 
though they are run at a slow speed, while an im- 
provement could be made in the exhaust ports, 
hence the conclusion that the steam port area 



36 MODERN EXAMINATIONS 

may be made 10 per cent, of the cylinder area, and 
exhaust port area 12 per cent, of it, with g'ood re- 
sults. 

The diameter of the crank shaft should be one- 
half of the diameter of the cylinder, in order to 
be stiff enoug-h to avoid springing, with its accom- 
panying evils. Of course it is easy to find en- 
gines that have them smaller than "this, and still 
give no trouble, but on the other hand, those 
builders who take pride in showing that they put 
plenty of stock into their product adopt the above 
rule for size of crank shaft. 

If a deep key seat is cut in this shaft it weakens 
it materially, and to avoid this, at least one 
prominent maker (and perhaps more) has the 
shaft made larger where the fly wheel is to be lo- 
cated, so that the key way does not make it weaker 
than the main part of the shaft. If the diameter 
of the crank pin is .25 of that of the cylinder, it 
will give good results. 

As the wrist pin is supported at both ends, it is 
not necessary that it should be as large as the 
crank pin, so far as strength is concerned, but to 
make the wear on these pins as nearly equal as 
possible, it is frequently the custom to make 
them of the same diameter or nearly so. 

The connecting rod should be .23 of the diame- 
ter of cylinder in the middle and .18 of it in its 
smallest parts, and in order to reduce what is 
usually called the ** angularity of the connecting 
rod" as much as possible, its length should be six 
times the length of the crank. 

Sometimes we find a connecting rod made solid 
at one end and with the ordinary strap and key at 
the other end. This is done to keep the length of 
the rod, or, more properly speaking, the distance 
between the centre of the crank pin and the 



OF STEAM ENGINEERS. 37 

centre of the wrist pin constant, for with the 
strap and key the wear tends to shorten this 
distance, and with the solid end it tends to 
leng"then it, so that it will always be the same, 
provided the brasses wear alike. 

The diameter of the piston rod should also be 
determined by the diameter of the cylinder, with 
perhaps some modification for very high steam 
pressures. With ordinary leng-ths in the case of 
a non-condensing- engine it should be made .15 of 
the diameter of the cylinder, for say 90 pounds 
or less, but if 130 pounds are to be required, .18 
of it will be necessary for safety. 

It is the custom of some of the builders of me- 
dium-sized machines to make the length of the 
main bearing the same as the diameter of the cyl- 
inder. This is a very liberal allowance, still it 
is not necessary or practicable in the case of 
large engines. 

The lengths of the eccentric and valve rods are 
determined by the size of the engine, and their 
diameters vary greatly, and always will, for with 
a style of valve that works easy a light rod will 
answer every purpose, but with the same size of 
engine having a different valve it may require rods 
nearly twice as large as in the former case. 
When we speak of a counterbore in a cylinder we 
mean that it is bored larger at each end for a cer- 
tain distance, in order that the packing rings, as 
they slide back and forth in the cylinder, may not 
leave a shoulder at each end of it, which in the 
course of time would cause a pound when the 
engine passes its centres. 

As the rings pass partially over the edge of this 
counterbore, it is plain that a shoulder cannot be 
left there until the main part of the cylinder is 



38 MODERN EXAMINATIONS 

worn to the full size of it, but by that time the 
cylinder will need reboring". 

Eng-ine builders frequently make the mistake of 
not counterboring" deep enough to allow the ring's 
to travel to it, which can sometimes be remedied 
by putting" in wider rings. 



OF STEAM ENGINEERS. 39 



CHAPTER VI. 

CONDENSING AND NON-CONDENSING ENGINES. — 

DESCRIPTION OF DIFFERENT TYPES 

OF ENGINES. 

It will probably be necessary to explain the dif- 
ference between non-condensing* and condensing* 
engines, by stating that with the former steam is 
exhausted ag^ainst the atmosphere, while in the 
case of the latter it is exhausted into a condenser, 
and the air pump removes the pressure of the air, 
the effect of which is to reduce the back pressure. 
This will naturally suggest the question as to 
what the back pressure on an engine is, to which 
the engineer should reply that the steam acting 
on the piston to drive it forward gives us the for- 
ward pressure, and as there is always some 
pressure on the opposite side of the piston which 
tends to oppose its advance, this is very properly 
called back pressure, and the difference between 
these two is called the mean effective pressure. 

In giving the amount of these different press- 
ures it is customary to state what the average is 
for the whole stroke, or in other words what the 
mean pressure is. When the term back pressure 
is used, it is generally understood to mean the 
back pressure above the pressure of the atmos- 
phere, as for instance when we say that our 
engine is working under four pounds back press- 
ure, caused by heating the factory w^ith exhaust 
steam, we mean that there is four pounds back 



40 MODERN EXAMINATIONS 

pressure above the atmosphere, but when mention 
is made of the back pressure absolute, we mean 
the total back pressure measured from a perfect 
vacuum. By initial pressure is meant the press- 
ure in the cylinder at the beg-inning* of the stroke, 
and by terminal pressure is meant the pressure 
existing- at the time that the exhaust valve opens 
to discharge the steam. 

The applicant for a license may be called upon 
to explain the difference between a throttling- and 
an automatic eng-ine, when he should reply that 
with a throttling- engine the point of cut-off is 
fixed, and the speed reg-ulated by a valve in the 
steam pipe, called the g-overnor valve, which 
admits more steam when the load is increased and 
less w hen it is decreased, but during- a fixed por- 
tion of each stroke (usually about three-quarters 
of it), while with an automatic engine the steam is 
admitted at nearly boiler pressure, and when suffi- 
cient has been admitted to complete the stroke it 
is quickly cut off. 

An adjustable cut-off eng-ine is one in which the 
speed is reg-ulated by throttling- the steam, and 
the point of cut-off is varied by means of a hand 
wheel on the outside of c\dinder. 

A compound eng-ine is one in which the steam 
is used in one cylinder, then exhausted into 
another, where it does more work, and is then 
exhausted into the atmosphere. A compound 
condensing- engine is a compound eng-ine with the 
condenser attached. 

A triple expansion eng-ine is one in which the 
steam is used in one cylinder (called the hig-h 
pressure cylinder) then exhausted into another 
called the intermediate, and then exhausted into 
another called the low pressure cylinder, and 
from thence into the atmosphere. If a condenser 




OF STEAM ENGINEERS. 41 

is attached it is said to be a triple expansion con- 
densing- engine. 

A quadruple expansion engine is one in which 
four cylinders are used, the same steam passing 
through all of them, and then into the air, and if a 
condenser is added, it is called a quadruple ex- 
pansion condensing engine. 

The advantages and disadvantages of these sev- 
eral types may be summed up as follows: The 
throttling engine is used extensively for small 
mills and factories, on account of its simplicity 
and low first cost, but it is very wasteful of steam, 
and could not be tolerated for large powers where 
fuel is worth anything. The automatic engine is 
usually more complicated and consequently more 
liable to become deranged than the throttling 
engine, but is more economical in the use of 
steam, and for medium powers is very satis- 
factory. When a condenser is added it increases 
the complication, but reduces the consumption of 
fuel. 

An adjustable cut-off engine is a kind of a cross 
between an automatic and a throttling engine, but 
can be used to advantage where the load is rea- 
sonably constant during a part of the day, and is 
increased to a certain known extent during the 
remainder of it, for in that case the cut-off may 
be varied to suit the load. It is not probable that 
they will ever come into very general use for 
stationary work. 

The compound engine is economical in the use 
of steam only when the load is just right for it, 
but is expensive to run if the load is too light, and 
cannot be used to advantage if the load is a very 
heavy one. It is also complicated, and the first 
cost of it is large. 

The compound condensing engine is coming 



42 MODERN EXAMINATIONS 

into very g-eneral use for large powers, on ac- 
count of its economy in the use of steam, and 
although it is complicated, and the first cost of it 
is very large, and intelligent supervision is abso- 
lutely necessary, still its economy more than 
overbalances these objections to its use. A high 
boiler pressure is essential to success. 

In the triple expansion condensing engine, the 
complication and first cost is increased, but 
owing to its greater economy it finds favor with 
some. The first cost of the quadruple expansion 
condensing engine is excessive, and the cost of 
keeping it in repair proportionately great. It 
requires the most intelligent supervision that can 
be procured, and its use is of necessity limited to 
the very largest powers, but where fuel is expen- 
sive it is a profitable investment. A very high 
boiler pressure is absolutely necessary in order 
to use the steam to good advantage. 

We sometimes wonder what sort of a machine 
the steam engineer of the future will be called 
upon to run. Will it have six, eight or ten cylin- 
ders? Just imagine an engine room containing 
an engine with ten cylinders, each one of which 
has four valves, with a total of 20 dash pots. It 
might do very well as long as everything is new 
and in good order, but how will it be when it has 
run for several years, with a record of only $1.37 
spent for repairs, and the boss positively declin- 
ing to make any that year, because business is 
dull? And then, as a matter of course, the boiler 
pressure will have to be increased to a frightful 
extent, and boiler plates will compare favorably 
with the armor plates for the new cruisers that 
will be in course of construction at that time. 
But some will say that we have now reached the 
limit for all these things, but do not be too sure 



OF STEAM ENGINEERS. 43 

of it, for you must remember that there were men 
who believed at one time that an engine could 
never be run at 150 revolutions per minute. 



44 MODERN EXAMINATIONS 



CHAPTER VII. 

MEANING OF THE TERM "HORSE POWER." 

The term "horse power" is one that is very 
commonly used, but at the same time there are 
many eng-ineers, or men in charge of steam 
plants, that do not thoroug-hly understand it. 

Let us take for our starting- point a small en- 
g-ine made in the usual way, except that instead of 
a fly wheel it has a drum on the crank shaft, on 
which is wound a small wire rope. We have a 
piece of cast iron which weig-hs 33,000 pounds. 
We attach the end of the rope to the weigfht, and 
start up our eng-ine, which runs at 50 revolutions 
per minute. We time the weight as it goes up, 
and find that it rises just one foot per minute, 
with a mean effective pressure of 20 pounds in the 
cylinder. This is just one horse power. 

Now suppose that we attach two pieces of cast 
iron, each weighing 33,000 pounds, to the end of 
our wire rope, and start up the engine. It runs 
until the slack of the rope has been taken up, 
when it stops, and we discover that we cannot 
raise the two weights together. We now proceed 
to take the drum off from the crank shaft and put 
a gear wheel on in its place. We next put up a 
second shaft, on which we put the drum, and also 
a gear wheel just twice as large as the one on the 
crank shaft. We now start up the engine with its 
speed of 50 revolutions, and a mean effective 
pressure of 20 pounds, as before; we find that we 



OF STEAM ENGINEERS. 45 

can just raise the two weights. Are we now 
using two horse power? 

Some will probably say yes, because we are 
raising just twice as much weight as we did be- 
fore, but in reality we are using just one horse 
power, as we did in the first experiment, for 
although we are raising twice the weight that we 
did before, it travels upward but one-half as fast, 
therefore the power consumed is the same in 
both cases. 

Now if we speed our engine up to 100 revolu- 
tions per minute with the same pressure as be- 
fore, our weights will travel upwards at the rate 
of one foot per minute, and then we shall be 
developing two horse power. If we increase the 
speed to 200 revolutions per minute with the same 
pressure, we shall raise the two weights at the 
rate of two feet per minute, and shall use four 
horse power to do it. 

We assume that the highest point of speed has 
been attained, and we still wish to do more work. 
Our next move is to increase our mean effective 
pressure to 40 pounds, and then we can raise four 
pieces of cast iron, each weighing 33,000 pounds, 
at the rate of two feet per minute, and shall con- 
sume eight horse power in doing it. 

By this explanation we trust that the meaning 
of the term "horsepower" is made plain, for it 
is 33,000 pounds raised one foot high in one min- 
ute, and it very naturally follows that to deter- 
mine the horse power of any engine we must 
ascertain the number of square inches in the sur- 
face of the piston, and multiply this number by 
the effective pressure acting on every square inch. 
This product must be multiplied by the number 
of feet that the piston travels per minute, and 



46 MODERN EXAMINATIONS 

when we divide the product so obtained by 33,000 
we shall know the horse power of the engine. 

We sometimes hear men say that they wonder 
how it is that such a small engine can do so much 
work, as for instance in the cases of the heavy 
road rollers that we see on our streets. The en- 
gines that drive them are small, but we do not 
always consider that while they are moving a 
heavy load still it travels but very slowly. If the 
same engine were put into a light wagon it could 
make it travel very swiftly, and few men that see 
it would consider it quite possible that it required 
fully as much power to drive the light wagon 
swiftly as it does to drive the heavy road roller 
slowly. 

We also hear men speak of putting on a small 
fly-wheel, and belting on to a large pulley on the 
main shaft, in order to get more power out of their 
small engine, but with a constant piston speed 
and mean effective pressure, the power of the en- 
gine is the same, regardless of the way in which it 
is connected to the machinery to be driven. 

In the foregoing illustrations the friction of 
the engine itself and of the gears was not spokea 
of, because it was unnecessary, for while it in- 
creases with speed and pressure, it has no effect 
on the raising of the weights, which represent the 
machinery in a factory. 

If a man says that he is running a 100 horse 
power engine, in reply to a question, what an in- 
definite answer it is. Take the case of the first 
illustration. There we had an engine of one 
horse power. In the last illustration we had an 
eight horse power engine, and yet it was just the 
same machine in both cases. It had not been en- 
larged in any of its parts, or strengthened in any 
way, and when it is shut down it will have exactly 



OF STEAM ENGINEERS. 47 

the same appearance in both cases, and yet one 
day it is a one horse power machine and the next 
it is eig^ht times as large, if we were to judg'e by 
its rating-. It is just so with larger engines, for 
the principle holds good with them, as with 
smaller sizes. 

If an engineer is asked how large an engine he 
is running, and replies that it has a 20-inch pis- 
ton, a 4-foot stroke, and runs at 65 revolutions 
per minute, with a boiler pressure of 90 pounds, 
he conveys an intelligent idea of the machine in 
his charge, and if he adds that the mean effective 
pressure is usually about 35 pounds, the reply is 
complete, but not otherwise. 



48 MODERN EXAMINATIONS 



CHAPTER VIII. 

CAECULATING THE HORSE POWER OF AN ENGINE. 
— SQUARE ROOT. 

The matter of fig'uring' the horse power of an 
eng"ine should be thoroughly understood by the 
applicant for a license, and by this we do not 
mean that he should simply know how to repeat 
the rule, but that he ought to be able to not only 
work out an example illustrating the workings of 
the rule, but if other questions are asked him on 
the subject he must be prepared to give a ready 
answer. To fully illustrate what is meant by the 
above, an example will be introduced here and 
worked out in full, so that it may te made plain. 
The horse power of an engine is required, the 
following data being given: Diameter of cylin- 
der, 18 inches; diameter of piston rod, 2.75 
inches; stroke, 42 inches; speed, 65 revolutions 
per minute; mean effective pressure, 35 pounds. 
To find the area of a piston 18 inches in diameter 
we multiply 18 by 18, and the product by .7854, and 
find our answer to be 254.46 square inches. The 
area of a piston rod 2.75 inches in diameter is 5.93 
square inches. Dividing this by two our quotient 
is 2.96. Subtracting this from the full area of the 
piston we have 254.46—2.96=251.5 square inches, 
which is the effective area of the piston. The 
area of the rod is to be deducted because the 
space occupied by it is not accessible for the 
steam to act upon, and we subtract but one-half 



OF STEAM ENGINEERS. 49 

of it because it is on but one side of the piston, 
the whole of the other side being- effective. Mul- 
tiplying- the area of the piston by the speed, and 
this product by the mean effective pressure, and 
dividing- by 33,000, we have 251.5 X 455x35 -f- 
33,000 = 121.37 horse power. This part of the 
problem is very easy to learn, but when it is pre- 
sented in another light, or perhaps it would be 
better to say that if other parts of data are g-iven, 
and other parts are to to be supplied by the can- 
didate, it may prove a stumbling- block to him, 
and undoubtedly will unless he has g-iven the 
matter some thoug-htful consideration. Suppose 
for instance, that he should be asked to state at 
what speed an eng-ine should be run whose cylin- 
der is 18 by 42 inches, with a mean effective press- 
ure of 35 pounds, in order to develop 121.37 horse 
power. In that case he would multiply 121.37 by 
33,000, and divide the product by the mean effect- 
ive pressure, and the quotient so obtained by the 
area of cylinder or piston, 121.37 X 33, 000 -^- 35-=- 
251.5=455 feet per minute. The piston travels 
seven feet per stroke and 455-^7=65 revolutions 
per minute. 

Suppose the question asked was, what the diam- 
eter of the piston should be if the stroke were 42 
inches, the speed 65 revolutions, the mean effect- 
ive pressure 35 pounds, and the horse power 
developed 121.37? In this case he would multiply 
the power developed by 33,000, and divide the 
product by the mean effective pressure, and the 
quotient so obtained bv the speed in feet per 
minute: 121. 37x33, 000 --'35 --445 = 251. 5. To this 
must be added one-half of the area of the piston 
rod, which is 2.96, and 251.5+2.96=254.46 square 
inches. Now in ascertaining" the area of the 
piston, we multiply the diameter of it by itself 



50 MODERN EXAMINATIONS 

and the product by .7854, consequently our next 
move in solving- the problem is to divide 254.46 by 
.7854 and the quotient is 324. 

We must now find the square root of 324. The 
following" rule for obtaining' the square root of 
any number that can be divided by four without a 
remainder is inserted here> because it will answer 
ever}^ purpose for man}^ of the numbers that en- 
g-ineers will use in making the above calculation. 
Divide the number by four and find the square 
root of the number so obtained. Multiply this by 
two and the product will be the desired square 
root. Applying- this rule to the case in hand we 
have 324-^4=81. This being' a small number it 
requires only a moment's consideration to show 
us that the square root of it is 9, and 9x2 — 18, 
therefore the square root of 324 is 18. If our cal- 
culation was for a 24-inch cylinder, the number 
that we wish to obtain the square root of w^ould 
be 576 instead of 324, and 576^4 = 144, and it 
needs but a moment to see that the square root of 
144 is 12, and 12x2 = 24. And even if our engine 
were a 30-inch one, it would still be convenient to 
use this rule, for the number would then be 900, 
and 900^4^:225, and the square root of 225 is 15, 
and 15x2 = 30. 

There are, however, other sizes, both larger 
and smaller than these, which this rule will not 
answer for as well, and for such we can use the 
following- rule for whole numbers: (1) Point off 
from right to left, in orders or places of twos. 
(2) Ascertain the highest root in the first order 
and place it at the right of the number, as in long- 
division. (3) Square this root and subtract it 
from the first order. To the remainder annex 
the next order and double the root already found 
and place it to the left ':^f this dividend. (4) As- 



OF STEAM ENGINEERS. 51 

certain how often this divisor is contained in all 
but the linal figure of the dividend, and place the 
quotient to the rig'ht of the root already obtained, 
and to the right of the trial divisor. (5) Multiply 
this divisor by the final figure in the root, and 
subtract as before. In like manner proceed 
until all the orders have been worked. In or- 
dinary business practice it is much more con- 
venient to take up a book of reference, which is 
usually at hand, and refer to the table containing 
the desired information, when the square root of 
a number is wanted; nevertheless, as this is some- 
thing of value to the engineer who wishes to 
become well posted, and as in the writer's opinion 
the rule, as given in some of the text books, is not 
readily understood, an explanation of its work- 
ings will be given in the next chapter. 



o2 MODERN EXAMINATIONS 



CHAPTER IX. 

TO INCREASE THE POWER OF AN ENGINE. EFP^ECT 

OF ADDING A CONDENSER. 

In order to illustrate the workings of the rule 
for extracting- square root of a number, and ap- 
plying- it to the case in hand, we will set down the 
number, which is 324, and our rule says: "First, 
point off from rig-ht to left in orders or places of 
twos." This bring-s our point between 3 and 2, 
g-iving- us 3 in the first and 24 in the second order. 
"Second, ascertain the hig-hest root in the first 
order," and that means to take the hig-hest num- 
ber which when multiplied by itself, the product 
will not exceed the number in the first order, 
"and place it at the rigfht of the number, as in 
long- division"; thus, 3.24(1. "Third, square this 
root," which means multiply it by itself, "and 
subtract it from the first order: 1x1 — 1 and our 
example is then as follows: 

3.24(1 

1 



2 
"to the remainder annex the next order" as 
follows : 

3.24(1 

1 



224 
"double the root already found, and place it to 



OF STEAM ENGINEERS. 53 

the left of this dividend." The root already 
found is 1, and when it is doubled we have 2, and 
having" placed it to the left of this dividend our 
example stands thus: 

3.24ri 

1 



2 j224 
*'Pourth, ascertain how often this divisor is con- 
tained in all but the final fig-ure of the dividend." 
Now the final figure of our dividend is 4, and leav- 
ing- this off we would naturally say that 2 is con- 
tained in 22, 11 times, but this is not proper here, 
for it can in no case exceed 9, and as we can only 
assume a number for this place, and try it, in 
order to know whether it is correct or not, let us 
try 9, and place the quotient to the right of the 
root already obtained, and to the right of the 
trial divisor. When we have done this our exam- 
ple stands thus : 

3.24(19 

1 



29)224 ^ 
*' Fifth, multiply this divisor by the final figure 
and subtract as before." This divisor is 29 and 
the final fig-ure in the root is 9, and 29x9 = 261. 
Now we cannot subtract 261 from 224, therefore 
we must try a lower number, and we will take 8. 
Our example is now as follows: 

3.24(18 

1 



28)224 
We now multiply 28x8 and our product is 224, 
which we subtract and find that we come out even, 
and the problem is solved : 



54 MODERN EXAMINATIONS 

3.24(18 
1 



28)224 
224 




The vsquare root of 324 being- 18, and therefore 
the piston must be 18 inches in diameter. 

Ag'ain, the diameter of the cylinder, the stroke, 
the speed and the horse power may be given, and 
the necessary mean effective pressure required. 
In this case we multiply the horse power devel- 
oped by 33,000, and divide the product by the 
speed, and this quotient by the area of the piston, 
the quotient so obtained being- the mean effective 
pressure. 121.37 x33,000-^455-^251.81=: 35 pounds. 
The horse power constant of an engine is found 
by multiplying- the effective area of the piston in 
square inches by its speed in feet per minute, and 
dividing- by 33,()00. The horse power may be de- 
termined bv multiplying- the horse power con- 
stant b}^ the mean effective pressure, if so desired. 
Sometimes an engine will not do the work re- 
quired of it, and it may be impracticable to 
increase the speed of it. In such a case if w^e can 
increase the mean effective pressure, we shall 
obtain more power w^ith which to drive machinery 
m direct proportion to the increase excepting- the 
increase in the friction of the eng'ine itself. This 
may be done bv increasing- the boiler pressure, or 
the size of the steam pipe, and making it more 
direct in reaching- the engine; by putting- on a 
more suitable governor; bv enlarging- the steam 
ports, or by lengthening the point of cut-off. To 
determine just which of these to do requires g-ood 
judg-ment, for it is quite plain that we shall not be 



OF STEAM ENGINEERS. 55 

able to remedv the evil unless we know just where 
the trouble lies. If we g'et boiler pressure ap- 
proximately up to our throttling governor, with a 
full load on the engine, we shall know that our 
steam pipe is large enoug'h, and if practicable the 
boiler pressure should be increased. 

If we get boiler pressure in our steam chest we 
shall know that our pipe and throttling governor 
are not at fault, but if there is less pressure in 
the cylinder than in the steam chest, either the 
steam ports are not large enough, or the valve is 
not set properly. If our slide valve cuts off the 
steam at half-stroke, we can increase the mean ef- 
fective pressure by cutting some of the lap off 
from it, thus allowing* the steam to follow during 
a g'reater portion of the stroke. If this is done 
it will be necessary to reset the valv e. The ques- 
tion as to whether we will have boiler capacity 
sufficient for the new conditions must receive at- 
tention before alterations are made. Adding a 
condenser will make it possible to increase the 
mean effective pressure, but does not of itself in- 
crease the said pressure. If the mean effective 
pressure cannot be increased, or the engine 
speeded up, the power of it may be increased by 
putting* on a larg'er cylinder, but of course this 
cannot be carried to any very g'reat extent, for it 
is only fair to assume that when the engine was 
built the several parts were calculated for each 
other, with a certain marg-in for safety, and if we 
increase the size of the c\dinder verv much, the 
stress mav be too great for some other part to 
bear, and a wreck be the result. When an eng'ine 
is overloaded, the best way is to remov^e it, and 
put in a new one, adapted to the load to be 
carried. 



56 MODERN EXAMINATIONS 



CHAPTER X. 

TO DETERMINE THE SPEED OF AN ENGINE BEFORE 
ADMITTING STEAM TO IT. — SIZE OF PUL- 
LEYS AND SPEED OF SHAFTING. 

Sometimes an eng-ine, especially if it be a small 
one, is shipped from the factory all ready to be 
put on to the foundation and belted up for use. 
In the absence of definite information, the pro- 
prietor would naturally ask the engineer that is to 
have charg-e of the machine how fast it is to run, 
and an inspector who is conducting" an examin- 
ation may ask a question, the reply to which will 
determine whether the engineer understands such 
matters or not. 

Of course any one could turn on the steam after 
the engine is ready to start, and when it is run- 
ning at full speed count the revolutions per minute 
and report the speed, but this may have to be de- 
cided on before the engine can be tried in this 
way. 

If the engineer will look the governor over 
carefully, he will find the number of revolutions 
that it is calculated to make stamped on it some- 
where, or at least this is the practice of the 
makers of the principal governors now used. 

The cut gears which transmit the motion of the 
governor shaft to the governor spindle and balls 
are both the same size, therefore they both 
> travel at the same speed. Now it should be re- 
membered that although the engine furnishes the 



OF STEAM ENGINEERS. 57 

power to run the g^overnor, still the g'overnor de- 
termines the speed at which the eng-ine runs. 
Prom this it will be seen that the speed of the 
g'overnor pulley is the standard, and from this we 
must make our calculations. 

Let us suppose for illustration that the g'ov- 
ernor pulley is seven inches in diameter, and is to 
revolve 150 times per minute, and the pulley on 
the shaft is ten inches in diameter. How fast will 
the eng-ine run? 150x7-^-10 ==105 revolutions per 
minute. 

Sometimes there is no g'overnor pulley on the 
eng-ine but the required speed is known, and the 
question is as to what the diameter of the g'ov- 
ernor pulley should be. Suppose that the eng-ine 
is to run 90 revolutions per minute, and the pulley 
on the shaft is 18 inches in diameter, and the g'ov- 
ernor is stamped 120; 90x18^120 = 13.5 inches, 
which is the diameter of the pulley needed for the 
governor. 

But if we knew the speed of the eng-ine and 
wish to find the speed of the g-overnor the calcu- 
lation would be 90 X 18 -^ 13. 5 = 120 revolutions per 
minute. By the above examples, the workings of 
the following- rules are illustrated. 

To determine the speed of the driven pulley, 
multiply the speed of the driver by its diameter, 
and divide the product by the diameter of the 
driven. The quotient will be the required speed. 

To determine the diameter of a pulley required 
to run a shaft at a g-iven speed, multiply the speed 
of the driver by its diameter, and divide the pro- 
duct by the speed of the driven. The quotient 
will be the required diameter. 

If there are two lines of shafting- already 
located with the pulleys on, and the necessary 



58 MODERN EXAMINATIONS 

Speed of the driven is kno^vn, and the required 
speed of the driver is desired, then multiplv the 
speed of the driven by its diameter, and divide 
the product by the diameter of the driver. The 
quotient will be the speed of the driver. These 
rules will enable the engineer to calculate the 
speed of any machine or line of shafting- in the 
mill or factory, excepting* that it does not take 
into account the slipping- of belts, and no rule can 
be formulated that will determine this accurately. 

These rules for calculating- the speed of shaft- 
ing- are based on the circumference of the pulleys 
over which the belt runs, althoug-h only the diam- 
eter is mentioned. This is done for simplicity, 
as when the diameters are used in both cases, the 
result is the same as if the circumference were 
broug-ht into the calculation. 

Suppose that we have one line of shafting- run- 
ning- 90 revolutions per minute on which is a 
pulley 36 inches in diameter. Prom this pulley, 
power is transmitted to another line of shafting* 
on which there is a 24-inch pulle3\ The belt con- 
necting* the two is 28 feet, three inches or 28.25 
feet long-. Now if we take off the belt and stretch 
it out on the floor, and take a pulley that is 36 
inches in diameter, and roll it along* leng-thwise of 
the belt, when we have traversed the whole leng-th 
of it, our 36-inch pulley will have revolved three 
times. If we take another pulley that is 24 inches 
in diameter and roll it over the belt in the same 
way, we shall see that it will revolve 4j^ times, 
therefore while the larg-e pulley revolves three 
times when on the shaft, the smaller one revolves 
Ayi times or 50 per cent. more. Fifty per cent, 
of 90 is 45, and 90+45 = 135, which is the speed of 
the 24-inch pulley. 

Or it may be done as an example in proportion 



OF STEAM ENGINEERS. 59 

as follows: The circumference of the 36-inch 
pulley is 9.42 feet, and that of the 24-inch one 6.28 
feet, and the larger one revolves 90 times per 
minute; therefore 6.28: 9.42: :90: 135. Ag-ain, if 
we work it out according* to the first rule g'iven 
for this purpose, we have 90x36^24 — 135, which 
demonstrates that all of the three ways are cor- 
rect. In this example we can readily see the end 
from the begfinning" without any fig-uring", but 
others involving* much different proportions may 
be worked out and proven in the same way. 



60 MODERN EXAMINATIONS 



CHAPTER XI. 

HOW TO CALCULATE THE MEAN EFFCTIVE PRES- 
SURE. — SEVERAL KINDS OF CRANKS. 



In determining* the horse power of an eng'ine, 
three factors are necessary, namely: area, speed 
and pressure. The first two are easily ascer- 
tained, and so is the third, provided you have an 
indicator to do it with, but if an engineer is 
requested to tell how he would decide this point, 
he should reply that it can be done if the initial 
pressure, point of cut-off and back pressure are 
known, or at least a g-ood estimate of it may be 
g*iven. There are two ways of doing* this, and 
one of them is to take the g-iven data, and from it 
lay out an indicator card, and then determine the 
mean effective pressure from it, but as the matter 
of laying" out the theoretical expansion line will 
be spoken of in detail in another part of this 
book, it will not be explained here. The other 
way to do it is by calculation as follows : 

The initial pressure and point of cut-off being" 
g-iven, divide the leng-th of the stroke in inches by 
the number of inches traversed by the piston 
before the steam is cut-off. The quotient will be 
the ratio of expansion. Find the hyberbolic 
log-arithm of this quotient, and add 1 to it. Di- 
vide the sum so obtained by the ratio of expan- 
sion, and multiply the quotient by the absolute 
initial steam pressure. Prom this product sub- 



OF STEAM ENGINEERS. 61 

tract the absolute back pressure, and the remain- 
der will be the mean effective pressure. 

For illustration let us take the case of an en- 
o-ine taking- steam at 80 pounds pressure, main- 
taining- it up to the point of cut-off, which takes 
place at one-quarter stroke, and assuming- that 
the valves and piston are tight. If the stroke of 
the eng-ine is 36 inches, and the cut-off at one- 
quarter stroke, then 36^4 = 9 inches, which is the 
distance travelled at quarter stroke; 36-=-9=4, 
which is the ratio of expansion. The h3^perbolic 
logarithm of 4 is 1.386, and adding one to it gives 
us 2.386, and 2. 386 -=-4 = .5965. The gage pressure 
being- 80 pounds, the absolute pressure is 80+14.7 
=94.7 pounds; .5965x94.7 = 56.488 pounds aver- 
ag-e absolute pressure. As we assume in this 
case that there is no back pressure above the at- 
mosphere, we must subtraxt the atmospheric 
pressure, and 56.488 — 14.7 = 41.788 pounds mean 
effective pressure. A procf of the correctness of 
this rule will be given in the part treating of indi- 
cator cards. Some further explanation of the 
above may be of interest. The term "ratio of 
expansion" means the number of times that the 
steam is expanded or increased from its original 
volume. Thus if the cut-off takes place at one- 
third stroke, by the time that the piston has 
reached the end of the stroke the steam occupies 
a space three times as large as it did when cut 
off (excluding- clearance), and the ratio of expan- 
sion is said to be three. If the cut-off takes place 
at one-half stroke it is two, etc. Hyperbolic 
logarithms are a series of numbers by which 
arithmetical calculations are simplified. The 
logarithm of a number is the exponent of a power 
to which 10 must be raised to give that number. 

The number 10 is used because it is a conve- 



62 MODERN EXAMINATIONS 

nient one, and not from necessity, as other num- 
bers mig-ht be taken as a base. To find the hyper- 
bolic log-arithm of a number, multiply the common 
log-arithm by 2.302585. Fortunately the books of 
reference which engineers use contain these in 
tabular form, so that no one thinks of fig-uring' 
them out in ordinary practice. In the above ex- 
ample the clearance is not taken into account, but 
when the rule is applied to any particular case the 
clearance in that case must be added to the 
stroke, and also to the space traversed by the pis- 
ton before the cut-off takes place, and it should 
be expressed in decimals of an inch. If the en- 
g-ine has a fixed or an adjustable cut-off, the point 
of cut-off may be determined by taking- off a cylin- 
der head, admitting steam to the steam chest, and 
turninof the en^-ine bv hand until the steam is shut 
off by the valve, when the distance may be noted 
on the guides. This should be done when the 
cvlinder is well warmed up, and the piston ring's 
may be tested by admitting steam to the oppo- 
site end, when the engine is on the centre. In 
the case of a slow-speed, long--stroke throt- 
tling engine, the initial pressure may be deter- 
mined by attaching- a steam gage to the steam 
chest, taking care to put a globe valve in the pipe, 
so that it mav be partially closed in order to pre- 
vent fluctuations of the pointer. 

The writer does not claim that the mean effec- 
tive pressure can be accurately determined in any 
other way than by using- a good indicator, but an 
approximation of it may be obtained as above 
stated. The elements of uncertainty are the 
tightness of the valve and piston under actual 
working conditions, the amount of compression, 
and also the exhaust opening. We all know what 
a crank is (althoug'h there are several kinds of 



OF STEAM ENGINEERS. 63 

them), but if we were asked to tell what it is, 
some of us might be at a loss for a term to ex- 
press our meaning, unless we should remember 
that it is a device for converting the reciprocating' 
motion of the cross head into the rotary motion 
of the shaft. Some people evidently believe that 
there is a great loss of power in using the crank, 
and have made efforts to introduce some other de- 
vice that will answer the same purpose, but so far 
without success, and as a consequence the exprevS- 
sion that "the man who tries to improve upon the 
crank is a greater crank than the crank ever 
w£is, " is sometimes made use of. 

The term "valve gear" is used to designate all 
of the rocker arms, rods, cranks, etc., which 
form the connection between the eccentric and 
the steam and exhaust valves. A misunderstand- 
ing concerning' this is sometimes the cause of 
ludicrous mistakes, as, for instance, when a cer- 
tain man was told that the valve gear of the engine 
needed repairs, he thoug'ht that the bevel gears on 
the lower part of the governor needed attention, 
and when told that they were all right, said that 
they were the only gears on the machine. 



64 MODERN EXAMINATIONS 



CHAPTER XII. 

RULES FOR DETERMINING THE WEIGHT OF FEY 

WHEEES. 

We have never discovered just why it was that 
a fly wheel received its name, but the fact remains 
that a wheel put on the crank shaft to answer the 
double purpose of helping* the engine to run 
steadv, and also to receive a belt for transmitting 
power, is so called. As the engine begins its 
stroke, it receives the steam at nearly the full 
boiler pressure. Soon it is cut off and begins to 
expand down, until when near the end of it there 
is but little pressure left, if the load is a light 
one. 

If there were no wheel on the shaft of a single 
engine, it would run at a very irregular speed, if 
it revolved at all, but as it is in practice the wheel 
causes the power stored up at the beginning of 
the stroke to be given out during the latter part 
of it, the result being economy in the use of steam 
and steady speed. 

After looking over the several specimens of fly 
wheels put on engines by their builders, we are 
caused to wonder if there has been any rule fol- 
lowed determining their size and weight. This is 
an open question, but nevertheless there are rules 
for this purpose which will give good results, 
one of which is as follows: 7,000,000--R2--D = P, 
in which R — revolutions per minute, D=diam- 



OF STEAM ENGINEERS. 65 

eter of wheel, and P the number of pounds per 
horse power required in the rim of the wheel. 

This rule recognizes the fact that the efficacy of 
a wheel increases, not as its velocity, but as the 
square of its velocit}^ and as its diameter. This 
is shown by the way that the constant number 
7,000,000 was obtained, which is as follows: An 
eng'ine having" a fly wheel which gave good results 
at a known load was taken, and dividing its weight 
by the horse power developed, and multiplying 
the quotient so obtained by the square of the 
number of revolutions per minute and by its 
diameter. 

Let us now explain and illustrate this rule, be- 
ginning by reading the formula as follows: 
Divide 7,000,000 by the square of the number of 
revolutions per minute, and the quotient b}^ the 
diameter of wheel. The quotient so obtained will 
be the number of pounds per horse power re- 
quired for the rim of the wheel. 

Por our example let us take the engine spoken 
of in Chapter 8, in which the diameter of c^dinder 
is 18 inches, the stroke 4-2, inches, speed 65 revo- 
lutions per minute, mean effective pressure 35 
pounds, and horse power developed 121.37. It 
w^ll be necessary to assume the diameter of the 
wheel, and for convenience sake we will call it 15 
feet. Apph^ing- the rule our first step is to square 
the number of revolutions per minute, and 65 X 
65=4225. 7,000,000^4225=1656.8, and dividing 
this by the diameter of wheel we have 1656.8^15 = 
110.45. The power developed is 121.37, and 
110.45 X 121.37= 13,405.3165 pounds. This it must 
be remembered is for the rim of the wheel. 

Let us look for a moment at the foundation on 
which this rule is based. Let us suppose that 
this fly-wheel had been made for this engine, and 



66 MODERN EXAMINATIONS 

is found to give good results. Taking this as a 
basis, we divide the weight by the power devel- 
oped, and multiply by the square of the number 
of revolutions, and by the diameter, 13,405.3165-^ 
121.37x4225x15=6,999,768.75. This is not quite 
as much as the constant number given, but the 
difference is due to the fact that the fractions are 
not carried out indefinitely. 

There is another rule which may be preferred 
by some, and it is used bv many of our designers, 
as follows: Divide 12,000,000 by the sq lare of 
the diameter of the wheel in feet, and this quo- 
tient by the square of the number of revolutions 
per minute, and m_ultiply this quotient by the area 
of the cylinder in square inches and by the stroke 
in feet. 

Applying this rule as before, we have 12,000,000 
-^ 225^4225x254.46x3.5 = 11, 221 pounds. This it 
should be remembered is to be the weight of the 
rim of the wheel, and is said to be sufficient to 
give good results for ordinary cases, but where 
the work is variable, as in rolling mills and some 
saw mills, the former is preferable, or may be 
exceeded, but it is well to bear in mind the fact 
that while in most cases where iron is used, to in- 
crease the amount of material used is to increase 
the strength of the machine, yet this does not 
apply to the rim of a fly wheel, owing* to the fact 
that when the weight is increased the tendency to 
burst is also increased. 

It may be well to speak of a rule for determin- 
ing the entire weight of wheel, and the following 
is one said to be used bv one of our most promi- 

D^X S 
nent engine-building firms : 785,400 — — =:W. 

D^XR^ 
d = diameter of cvlinder in inches, S = stroke in 



OF STEAM ENGINEERS. 67 

inches, D = diameter of wheel in feet, R = revolu- 
tions per minute. 

This formula sig'niiies that the constant whole 
number 785,400 is to be multiplied by a fraction 
whose numerator is found by multipl3dng' the 
diameter of the cylinder in inches by itself, and 
the product by the stroke in inches. 

The denominator is determined by multiplyino* 
the diameter of the wheel in feet by itself, and 
also by the square of the number of revolutions 
per minute. The final product will be the weight 
of the entire wheel. 

Applying' this rule or formula to the case in 
hand we find the square of the diameter of the 
cylinder in inches to be 324. The stroke is 42 
inches, and 324x42=13,608, which is the numer- 
ator of the fraction. The diameter of the wheel 
is 15 feet, and the revolutions per minute 65, 
therefore 15x15x65x65=950,625, which is the 
denominator, and the fraction then reads 

13,608 



950,625 
and by dividing- each part by nine, or in other 
words by cancellation, it mav be reduced to 

1512 ^ 



105,625 

In order to multiply our constant whole num- 
ber by this fraction, we must multiply it by the 
numerator and divide the product so obtained bv 
the denominator: 785,400x1512^105,625=11242.8 
pounds for the entire wheel. 

We g-ive these rules just as we find them, trust- 
ing* that the examples have been worked out in 
such a way as to be plain and easily understood 
by the engineer of limited education, in order 



68 MODERN EXAMINATIONS 

that he may make comparisons for himself. The 
first one is from a well known authority, while 
the second and third are from another source 
usually accepted as reliable. 

The results obtained differ widely, and it is 
proper that they should, for no one rule will apply 
to every case, for if we have a long-stroke, slow- 
speed eng-ine, running- a rolling- mill or a sawmill, 
or any other kind of a mill where the load varies 
g-reatly, it will need a heavier wheel than a hig-h 
speed eng-ine running- a dynamo or any other ma- 
chinery that operates in such a way as to make 
the load practically constant will; therefore, 
when a wheel is desig-ned, the kind of work that it 
is intended for must be taken into consideration. 

If the rim of a sound wheel is never run at a 
g-reater speed than 5000 feet per minute it will be 
within safe limits, but in desig-ning- a plant it 
would be well to make it less than this if possible. 

All fly wheels should be carefully balanced be- 
fore being- put into service, as it will tend to 
cause the engine to run steadier, the bearing's to 
run cooler, and the wheel will be safer. In bolt- 
ing- tog-ether the sections of a wheel, g-ood judg-- 
ment should be used, in order to avoid unneces- 
sary stress in screwing- up the nuts. 



OF STl^AM ENGiNEER&3. 69 



CHAPTER XIII. 

BEFORE AND AFTER ADDING A CONDENSER. — IS THE 
MEAN EFFECTIVE PRESSURE EFFECTED BY IT? 

Reference has been made in a preceding- chapter 
to the practice of adding' a condenser to a non- 
condensing engine, and as the candidate for a li- 
cense will probably be called upon to answer 
some questions concerning- this appendag-e to an 
engine, he should g-ive the matter some attention. 

In a certain work on steam eng-ineering, which 
lies before me, I find the statement that in ordi- 
nary practice if we add a condenser we shall raise 
the mean effective pressure by 12 pounds. This 
authority does not tell us what becomes of this 
increase of 12 pounds, or how we can use it up. 

A careful consideration will show any one that 
to run a certain machine will require a certain 
mean effective pressure in the cylinder, and 
whether we have a condenser in use or not does 
not affect this pressure in the least. If we start 
up another machine the mean effective pressure 
will be increased at once, and it will be just the 
same whether we use a condenser or not. This 
refers to ordinary practice. 

If, however, we had an engine using steam 
whole stroke, and maintaining boiler pressure up 
to the end of the stroke, running* non-condensing- 
and without a g-overnor, then by adding- a con- 
denser we could increase the mean effective press- 
sure by putting on a condenser, but this is not 



70 MODERN EXAMINATIONS 

ordinary practice, and in fact is seldom, if ever, 
found in every-day use. 

Assuming- this to be the case, the percentage 
of g-ain in pressure may be calculated as follows: 
Multiply the reduction in back pressure by 100, 
and divide by the mean effective pressure. Sup- 
pose that our boiler pressure is 80 pounds, and 
our mean effective pressure 80 pounds also. We 
reduce the back pressure by 12 pounds and 12 X 
100=1200, and dividing- 1200 by 80 gives us 15, 
which is the percentag-e of g-ain in mean effective 
pressure. The above conditions are the only 
ones under which a condenser adds to the mean 
effective pressure. 

In ordinary practice, if our initial pressure is 
80 pounds and our cut-off at one-third stroke, if 
we add a condenser and thereby reduce the abso- 
lute back pressure by 12 pounds, our g-overnor 
immediately reduces the forward pressure by 12 
pounds, and as the mean effective pressure is 
always the difference between the forward and 
the back pressure, and they are both reduced 
alike, the mean effective pressure is just the same 
as it was before. This is a theory that has been 
proven to be correct in practice, many times over. 

If it is desired to know how much the addition 
of a condenser will allow us to reduce the boiler 
pressure, and maintain the orig-inal point of cut- 
off, the following- is a simple formula for express- 
ing- it : 

PxS 



p'X(H. P.+l) 
in which P =mean effective pressure, S stroke in 
feet, p'= point of cut-off, plus clearance expressed 
in feet, H. P. = hyperbolic log-arithm of ratio of 
expansion, P' =boiler pressure. 



OF STEAM ENGINEERS. 71 

It sig*nifies that the mean effective pressure 
multiplied by the stroke in feet will g-ive us what 
we may term our first product. The point of cut- 
off, or in other words the distance travelled by 
the piston before the cut-off valve closes, in feet, 
plus the clearance, multiplied by the hyperbolic 
log-arithm of the ratio of expansion plus 1, will 
o-ive us our second product. Dividing* the first 
product by the second gives us the desired boiler 
pressure. 

Now if we assume that the initial and boiler 
pressure are both 80 pounds, the cut-off at one- 
quarter stroke, and not taking the clearance into 
account, which will affect the result but a very 
little, the mean effective pressure will be 41,788 
pounds. The stroke is 3.5 feet and the cut-off is 
at one-quarter stroke. 3.5-^4=. 875. The ratio 
of expansion is 4, the hyperbolic logarithm of 
which is 1.386 adding 1 to it equals 2.386. The 
problem is then as follows: 
41.788x3.5 

= 70 pounds. 

.875x2.386 

It is assumed that the condenser will reduce 
the absolute back pressure by 12 pounds. 

In case that the question is asked, as to how 
much the consumption of steam will be reduced by 
adding a condenser, maintaining' our initial press- 
ure, the answ^er is expressed in the following for- 
mula, assuming- the ratio of expansion to be six. 
Iv-i-R=l, in which L equals length of stroke in 
feet, R equals ratio of expansion ^assumed), 1 
equals point of cut-off in feet. Applying" this to 
the case in hand, we find that 3.5-^6 =.583 feet, or 
.583 of 12 inches equals 6.996 inches. By this we 
see that whereas the steam followed the piston for 
10.5 inches of the stroke before the condenser 



72 MODERN EXAMINATIONS 

was made use of, it is now cut off at 6.996 inches, 
and therefore the volume admitted is less in direct 
proportion. 

If we were to calculate the amount saved fi.g'ur- 
ing" from these two volumes, we should have a 
simple problem in proportion, as the whole stroke 
would be taken as 100. 10.5: 6.996: :100:66.6. 
This is solved by multiplying- 6.996 by 100 and 
dividing- the product by 10.5. In other words, 
the consumption of steam would be reduced from 
100 to 66.6 per cent., a saving of 33.4 per cent, on 
the face of it, as we sometimes say. 

It is possible that this would not be realized in 
practice, for while the volume admitted, as shown 
by the indicator, is as above stated, still, as the 
terminal pressure is less, the condensation would 
be more, which of course would effect the saving- 
in coal. 

In regard to the formula for determining the 
point of cut-off we would say, that as we have but 
one factor to start with, namely the length of the 
stroke in feet, and from this we must ascertain 
the other two, it is necessary to assume one of 
them and try it. If it does not prove to be cor- 
rect we must try another. In this case we as- 
sumed the ratio of expansion to be six, and the 
way to prove whether it is correct or not is as 
follows: Taking- the data which we now have, we 
must determine the mean effective pressure from 
it, by the rule given in Chapter 11 of this book. 
The cut-off is at one-sixth stroke, therefore the 
ratio of expansion of 6. The logarithm of 6+1= 
2.7918 and dividing by six we have .4653 as a quo- 
tient. The initial pressure is 80 pounds by the 
gage, to which we must add the atmospheric 
pressure; 80+14.7=94.7, and .4653x94.7=44.06 
pounds mean pressure. If the condenser re- 



OF STEAM ENGINEERS. 73 

moves 12 pounds of the back pressure due to the 
atmosphere, we shall 2.7 pounds left, and 44.06 — 
2.7=41.36 mean effective pressure. As it origin- 
ally was 41.788 pounds, the difference is but a 
fraction of a pound, and is practically identical. 
If it was not we should have to assume another 
ratio of expansion and try ag'ain. The author 
would state, in parenthesis, that he has indicator 
cards in his possession which prove these con- 
clusions to be correct in a remarkable degree. 



74 MODERN EXAMINATIONS 



CHAPTER XIV. 

SAFE WORKING PRESSURE OF A STEAM BOILER. 

Having- devoted a larg-e portion of the preceding- 
chapters to answering- questions concerning- the 
eng-ine, we will now turn our attention to the 
boiler, but in doing- this what a transformation we 
have made. Prom the contemplation of the brig-ht, 
symmetrical eng-ine, we turn to the black, sooty 
and dirty boiler, but the man who aspires to be a 
licensed eng-ineer and to hold a first-class certifi- 
cate to that eifect, will find that there are many 
questions to be answered concerning- the "source 
of power," and that a knowledg-e of its construc- 
tion, the streng-th of the materials of which it is 
constructed, the comparative streng-th of the 
seams, of the manner in which it is braced, and 
other points concerning- it will be necessary. The 
first thing- that we will take up for consideration 
in detail will be the way to calculate the safe work- 
ing- pressure of any boiler. 

For illustration suppose that a boiler is made 
of iron three-eig-hths of an inch thick, the long-i- 
tudinal seams are double riveted, and the diameter 
of the shell is 60 inches. To this case the follow- 
ing- formula for determining- the safe working- 
pressure of a double riveted boiler will apply. 
Tx. 70x10,000 



R 

safe working- pressure, in which T= thickness of 
iron in decimals of an inch, and R= radius, or 



OF STEAM ENGINEERS. /O 

one-half of the diameter. Then .375 X .70x10,000 
-f- 30= 87.5 pounds safe working- pressure. Our 
first step in solving- this problem is to reduce Ys 
to decimals of an inch by setting- down 100 and 
dividing- it b}^ the denominator of the fraction, 
which in this case is eig'ht, and adding* ciphers to 
our dividend (100) until we can divide by eig-ht 
without a remainder. We find that by adding- one 
cipher our quotient is .125, which is one-eigfhth of 
an inch expressed in decimals, and by mtiltiplying- 
by three we have .375. 

This may also be done by adding- ciphers to the 
numerator and dividing- by the denominator. By 
adding- three ciphers, we can divide without a re- 
mainder and by pointing- off as many decimals in 
our answer as we have added ciphers we g-et the 
same result, 3,000-^8= .375 as before. 

We do this because the streng-th of boiler plate 
is estimated at a certain amount per square inch 
of sectional area, or in other words, a bar one 
inch square will require a certain amount of stress 
to cause it to break in two. As our plate is but 
three-eig-hths of an inch thick, it is proper that we 
should take that as a basis for our calculation. 
We multiply by .70 because the riveted seam is 
never as strong- as the solid plate, and where there 
are two rows of rivets it is estimated to possess 
.70 of the streng-th of the solid plate. We next 
multiply by 10,000 because g-ood boiler iron has a 
tensile strength of 50,000 pounds to the square 
inch of sectional area, and taking- one-fifth of this 
for a safe load g-ives us ihe number 10,000. 

If the tensile streng-th is 60,000 pounds and the 
factor of safetv 5 then we should have 60,000-i-5= 
12,000 instead "of 10,000 and if it is 40,000, then 
40,000--5 =8,000 pounds. The number that we 



76 MODERN EXAMINATIONS 

divide the tensile strength by is called the factor 
of safety. 

"We divide b}^ one-half of the diameter, because 
in this case we have calculated the streng-th of but 
one side of the boiler, taking- one inch of its leng^th 
and therefore must not calculate on the whole 
diameter. This rule is probably as g-ood a one as 
can be found, as it takes into consideration all of 
the elements in the case except one, and that is it 
does not recog-nize the fact that all double-riveted 
seams do not possess the same streng-th. It is 
g-iven to us in this form because Fairburn found 
by experimenting* with double riveted seams that 
30 per cent, of the streng-th of the solid plate was 
lost in punching-, but this does not g-o to show 
that all seams are alike, simply because they have 
two rows of rivets in them. 

Having- g-iven a rule which the writer considers 
to be a g-ood one, he wishes to speak of some 
others, and express an opinion concerning* them. 
Here is one that is published by a firm whose 
name is calculated to inspire confidence. Multiply 
twice the thickness of the iron by the tensile 
streng-th of sheet, and divide the product by diam- 
eter of shell in inches. Divide this product by 
six. For double riveted seams add 20 per cent. 
This rule apparently assumes that it is safe to 
carry but one-sixth of the bursting- pressure in 
every-day practice, but when we examine a little 
closer, we find that it is not as safe as it looks to 
be. It will be noted that the whole streng-th of 
the sheet is taken, no deduction being- made for 
the loss of streng-th due to the sing-le riveted joint. 
With this rule the factor of safety is but 3.5, 
which we consider altog-ether too small for the 
averag-e boiler. 

For the purpose of comparison, let us assume 



OF STEAM ENGINEERS. 77 

the elements of the preceding- case and try it. 
Thickness of iron, .375; tensile, 50,000 pounds; 
diameter, 60 inches. Applving- this rule, we have 
.375 X 2 x50,000^60--6= 104.16 pounds for a boiler 
with sing*le riveted seams. Adding- 20 per cent, 
for double-riveted seams, we have 104.16+20.83= 
124.99 pounds for safe load. Would not the aver- 
ag-e intellig-ent eng-ineer doubt the expediencv of 
carrying" 125 pounds pressure on such a boiler? 
Another authority g-ives us the following- formula: 

SBt2 

=P 

DC 
in which 

S= tensile strength of plate. 
B= strength of joint. 
t= thickness of plate. 
D= diameter of shell. 
C= coefficient of safety. 

The ^'coefficient of safet}^" means the "factor 
of safety" which we assume to be 5. 

Now this formula, although it looks rather com- 
plicated, is really not so when explained. If we 
assume the elements of the preceding case it 
would stand as follows: 
50.000 X. 70 X. 375x2 

• =87-5 pounds. 

60x5. 
It will thus be seen that this rule is identical with 
the first one quoted, although it appears in quite 
a different way. 

The following rule is also given us for determ- 
ing the safe working pressure. Divide the thick- 
ness of the plate in inches by the diameter of the 
boiler in inches, and multiply the quotient bv 
7600 for an iron boiler with single riveted seams, 
and 9000 for double riveted seams. Applying- 



78 MODERN EXAMINATIONS 

this to the case in hand we have .375-^60x9000= 
56.25. Probably this is a "safe" pressure to 
carry on such a boiler, judg-ing- by the pressures 
that are safely carried on such boilers in every- 
day practice. Here are four rules g^iven us for 
determining- the pressure that it is safe to carry 
on a boiler of g-iven dimensions, which g^ives us 
three widely different results, and which of these 
are we to adopt? The first and third rules, g-iv- 
ing" 87.5 pounds for an answer, are undoubtedly 
the proper ones to adopt. The second one shows 
the eifect of competition as to who can allow the 
hig-hest pressure to be carried without disaster, 
while the fourth one is many years behind the 
times, and is not consistent with g'ood practice. 

We cannot tell how hig-h a pressure it is safe to 
carry until we know the actual streng^th of the 
seams based on the size and pitch of rivets, etc. 
In Chapter 15, due attention will be g-iven to this 
important factor, as in the preceding- cases we 
have only assumed that the seam possessed 70 per 
cent, of the streng-th of the solid plate. 

In a certain book, claiming- to g-ive correct rules 
and instructions to eng-ineers and firemen, I find 
the following-: "Rule to find ag-g-regate strain 
caused by the pressure of steam on the shells of 
boilers. Multiply the circumference in inches by 
the leng-th in inches; multiply this answer by the 
pressure in pounds." 

This is incorrect, for while such a rule will g-ive 
the total pressure on the shell of a boiler, it is not 
a proper way to determine the strain (stress) on 
the shell, as that is determined by multiplying- the 
diameter in inches by the leng-th in inches. 



OF STEAM ENGINEERS. 79 



CHAPTER XV. 

STRENGTH OF THE SEAMS IN A BOILER. 

In considering' the streng'th of any riveted seam, 
it is very plain that it cannot be taken at an^^thing 
more than the weakest part of it. This may be in 
the rivets or it may be in the plate, or rather what 
is left oi it after it is punched or drilled. No 
joint can possess more streng-th than that due to 
the material left between the first row of holes, 
for it will make no difference whether there are 
one or two additional rows of rivets. The double 
welt butt joint owes its efficiency to this fact 
larg'ely, for in this case the rivets in the first row 
ma}^ be set wide apart, thus increasing* the net 
section of plate at this point. 

Suppose that we take up the illustration used in 
Chapter 14, in which the plate was 3-8 or .375 
thick, the tensile strength of it 50,000 pounds, and 
assume the pitch of the rivets to be 3 1-16 inches 
(3.0625 inches) their diameter, when in position, 
15-16 or .9375 inch. Now the pitch of the rivets 
mean the distance from the centre of one rivet 
hole to the centre of the next one, therefore when 
we wish to calculate the streng-th of this section 
of the plate, before the holes are punched, we 
must multiply the width of it by its thickness, 
which will gfive us the sectional area, and by mul- 
tiplying* the product so obtained by the tensile 
streng*th of iron, we shall have the streng-th of 
the section of solid plate. 

After the holes have been punched, as one-half 



80 MODERN EXAMINATIONS 

of each hole is included in the section designated 
by the pitch of rivets, we must deduct the diam- 
eter of one hole from the section, when we wish 
to calculate the strength of what is called the net 
section of plate. Illustrating- the above ideas we 
have 3.0625 X. 375x50,000 =57,421 pounds, which is 
the strength of the solid plate. Deducting the 
diameter of one rivet hole, we have 3.0625 — .9375 
X. 375x50, 000 =39, 843 pounds, strength of net 
section of plate. As we have now determined the 
strength of plate, at seam, let us calculate the 
strength of the rivets in the joints. In the sec- 
tion that we have taken there are two rivets in- 
cluded, for although in taking the pitch of the 
rivets, we include but one-half of two rivets in the 
first row, still, as there is another rivet directly 
between these two located in the second row, we 
must calculate on two rivets. The area of one is 
.69 and 69x2=1.38. If we take the strength of 
the iron in the rivets as being the same as that in 
the plate we must multiply 1.38 by 50,000 and our 
product is 69,000 pounds, which is the strength of 
the rivets. 

Again we find a difference of opinion among' ex- 
perts, for while some tell us that the iron in 
the rivets should be taken as the same as 
that in the plate, others claim that it is less, put- 
ting' it about .8 of it. If we should adopt this 
idea, we must multiply 69,000 by .8, giving' us a 
product of 55,200 pounds as the strength of 
rivets. The net section of plate is therefore the 
weakest, and by dividing 39,843 by 57,421 our quo- 
tient is found to be .69, or in other words, our 
double-riveted seam possesses 69 per cent, of the 
streng'th of the solid plate. In our original cal- 
culation we assumed it to be 70 per cent., which is 
near enough for practical purposes, under the 



OF STEAM ENGINEERS. 81 

conditions named, but if the rivets were larg-er or 
smaller, or had a different pitch, the results 
would be different as a matter of course. By this 
we see that all the details of the joint must be 
given before we can tell the strength of it. 

Another rule for determining strength of net 
section of plate is expressed by the following 
formula: 

P-D 

=Plate, 

P 
in which P equals pitch of rivets and D equals 
diameter of holes. Applying this to the case in 
hand, we have 

3.0625— .9375 

• =69 per cent, of solid plate. 

3.0625 
Another rule for determining streng-th of rivets 
is expressed bv the following formula: 
AxR 

— =Rivets, 

PXT 
in which A equals area of rivets, R equals number 
of rows, P equals pitch of rivets and T thickness 
of plate. Apph^ing this to the joint that we have 
been considering, we have: 

.69x2 



3. 0625 X. 375 
eq vials 1.2 times the strength of solid plate. 

We have already shown that the strength of the 
section of plate is 57,421 pounds and 57,421x1.2= 
68,905 or very nearly 69,000 pounds as before. 

This shows that the net section of plate is 
the weakest, as did our former calculation. 
These rules do not apply to the double welt butt 
joint, as now made for boilers of larg'e diameter, 



82 MODERN EXAMINATIONS 

calculated to carry high steam pressures, for the 
first row of rivets are spaced much farther apart 
than is ordinarily done, or in other words given a 
greater pitch. 

The effect of this is to greatly increase the 
strength of the weakest part of the joints, namely 
the section of plate between the rivets, in the first 
row. Under any circumstances liable to be found 
in practice, the rivets in this joint are much 
stronger than the plate is, but if it is desired to 
calculate the strength of rivets it may be done by 
taking a section extending from the centre of 
rivet in the first row to the centre of the next one 
in the same row, and estimate it as a single-riveted 
joint. To this must be added the strength of the 
rivets in the second and third rows, for a section 
of the same width, and add the two together. In 
order to familiarize himself with these calcula- 
tions, the candidate for a license should practice 
on different problems along this line, supplying 
data himself. 



OF STEAM ENGINEERS. 83 



CHAPTER XVI. 

BRACING FLAT SURFACES IN A BOILER. 

In the ordinary tubular boiler, the longitudinal 
seam is the one by which the strength of the 
whole structure is usually calculated, for the 
tubes strengthen the heads greatly, and from the 
nature of the case the curvilinear seams are sub- 
jected to much less stress than the others are. 
There is, however, a space on each head above 
the tubes, which must be held by braces, aud also 
a space below them in those boilers which have a 
manhole in lower part of front head, as all of 
them should have. It is a very good plan to have 
these braces extend from one head to the other, 
as they strengthen the shell in that case, without 
adding any unnecessary stress to the iron in the 
braces. Another reason is that they then are in 
a position to hold to the best advantage, as a 
brace standing at an ang-le greater or less than 90 
degrees cannot hold as much stress on the heads 
as one that stands at right angles to the heads. 
Where they are put on from head to shell, their 
efficiency decreases as their length is made less, 
which fact is not always taken into consideration, 
judging by the way some boilers are constructed. 

In designing this part of a tubular boiler, it is 
necessary to take into consideration the surface 
to be braced, the pressure that it will be called 
upon to withstand, and the size of the braces. 
We are told that braces in a steam boiler should 
not be made to withstand a pull exceeding 6,000 



8-1- MODERN EXAMINATIONS 

pounds per square inch of sectional area. If 
braces were made of iron one inch square it 
would be much less trouble to estimate their 
capacity, but as they are usually made of round 
iron, it is necessary to reduce them to square 
inches. A piece of round iron l}i inches in diam- 
eter contains a square inch of iron, practically, 
but if a brace is made of round iron 1.5 inches 
in diameter we must ascertain its area by squaring- 
its diameter and multiplying- by .7854, thus: 1.5 X 
1. 5 X. 7854 = 1. 767 square inches. Now if each 
square inch of section may be depended upon to 
bear a stress of 6,000 pounds, in order to ascer- 
tain how much it will do to put on a brace 1.5 
inches in diameter, we must multix3ly 1.767 by 
6,000, and our product is 10,60^ pounds. 

Suppose that we find that we have a flat surface 
on one of our boiler heads, containing- 700 square 
inches of surface, and we wish to carry 90 pounds 
of steam pressure. By multiphnng- 700 by 90 we 
find that we have a load of 63,000 pounds to pro- 
vide for, and as each brace will hold 10,602 
pounds, by dividing- 63,000 by 10,602 our quotient 
is found to be 5.94, therefore we shall need to put 
in six braces, in order to make the head safe. 

Braces should be very carefully inspected be- 
fore being- put into service, in order to guard 
ag-ainst defects in the iron, especially where they 
are welded, and we note with pleasure that braces 
are now in the market that have no welds in them, 
as we believe that this is a step in the rig-ht direc- 
tion. 

We wish to call attention to the fact that in cal- 
culating- the stress on a brace extending- from 
head to head, it is proper to take the surface on 
one head only, and not on both of them. This 
does not seem to be g'enerally understood by en- 



OF STEAM ENGINEERS. 85 

g-ineers, althong-h much has been said on the sub- 
ject. The writer recalls an instance where he 
made this statement before a society of en- 
g-ineers, and one of them remarked in an exceed- 
ing-ly sarcastic manner that in his boiler there was 
a pressure on both of the heads. Well, what of 
it? We never doubted the truth of the state- 
ment, but as that fact has no bearing" on the idea 
that in calculating- the load on the brace, we must 
take the surface on one head only, we made no 
reply. 

If the brace extends from head to shell, there is 
just as much stress on it as if it extended from 
head to head. A brace should never be put from 
head to shell on the lower part of a tubular boiler, 
for where it is riveted to the shell it makes a place 
for scale to collect, and the flat part of a brace so 
put in prevents the water from coming- in contact 
with the iron of the shell, and that too in about 
the hottest part of the boiler. 

It is customary to rivet pieces of T iron to the 
flat head to be braced and then attach the braces 
to them. This, of course, g-reatly streng-thens 
the heads, and makes a g-ood anchoragfe for one 
end of the braces. 

It may not be out of place here to remark that 
where the rivet holes are drilled the sheets are 
strong-er than where they are punched, because 
punching- disturbs the fibres of the iron, but 
when drilled the edg-es of the holes are more 
sharply defined, therefore the rivets will shear 
more easily. 

However, the difference is in favor of the drilled 
holes. In calculating- the area of a boiler head to 
be braced it is not necessary to take into consid- 
eration the whole surface exposed to pressure, 
for the flanges impart stiffness to it, to a limited 



86 MODERN EXAMINATIONS 

extent, according- to the thickness of the head. 
If it is 9-16 or ^^ inch thick it will do to leave a 
space of two inches from the shell, out of the cal- 
culation. This will receive further consideration 
in another chapter. 



OF STEAM ENGINEERS. 87 



CHAPTER XVII. 

THE HORSE POWER OF A BOILER. — PRIMING AND 
FOAMING. 

This book would not be complete unless it con- 
tained instructions as to the proper way to calcu- 
late the horse power of a boiler. We occasion- 
ally see it stated in print that in the case of a 
tubular boiler 15 square feet of heating- surface 
constitutes a horse power. This may be correct 
and it may not be, for it will depend much on 
other conditions. In a preceding- chapter the 
proper way to calculate the horse power of an 
engine was illustrated and explained. Prom the 
data there given it will be seen that while the size 
of the cylinder is an important factor in solving- 
the problem, still that of itself does not determine 
the horse power of the engine, but other things 
must be taken into consideration. 

The square inches on the inside surface of the 
cylinder does not tell us the power of the ma- 
chine, neither does the square feet on the outside 
surface of a boiler tell us the power of it, for in 
either case it will depend on how much heat is ap- 
plied, etc. The only proper way to determine the 
horse power of a boiler is by the amount of water 
that it will evaporate per hour under given condi- 
tions. It will evidently make a difference whether 
this water is to be evaporated into steam of 10 
pounds pressure or of 150 pounds pressure, for 
in one case it will require much more heat than in 
the other. 



bo MODERN EXAMINATIONS 

Ag-ain, it will make a difference whether the 
water to be converted into steam is hot or cold 
when it is delivered into the boiler. If it is put in 
at a temperature of 40° it will need more heat to 
convert it into steam than it will if it enters at 
212°. From this it will be seen that some stand- 
ard must be adopted in order to bring- all of the 
different conditions under which boilers are run, 
to a common basis for the purpose of comparison. 
The standard usually adopted is the evaporation 
of 30 pounds of water per hour from a tempera- 
ture of 100° into steam at 70 pounds pressure. 
Now ag-ood tubular boiler, well set and properly 
run, will develop a horse power for each 15 square 
feet of heating- surface without doubt, and some 
of them are developing- nearly two-horse power 
for each 15 square feet of heating- surface, while 
others require 20 or more. Some firms who man- 
ufacture boilers allow one square foot of g-rate 
surface for each 36 feet of heating- surface, and 
this works very well in practice. 

The candidate for a license should bear in mind 
that no inflexible rule can be g-iven for determin- 
ing- the heating- surface of a boiler, as, for in- 
stance, some writers say take one-half of the sur- 
face of the shell of the boiler and two-thirds of 
the heads. This is evidently a mistake, althoug-h 
perhaps not a very serious one in its conse- 
quences, for if the brick setting* does not come in 
contact with the shell until it is above the centre 
line of boiler, then more than one-half of the 
shell is available as heating- surface. Many boilers 
are set in this way. To this should be added the 
internal surface of all of the tubes or flues. 
Ag-ain the area of one head up to the water line 
should be determined, and the combined area of 
the holes cut for the tubes subtracted from it. 



i 



OF STEAM ENGINEERS. 89 

This will g'ive the heating" surface in the heads 
when multiplied by two. 

The water space of the boiler is that part of it 
which is occupied by the water, and is found by 
ascertaining- the area of one head up to the water 
line, as before referred to, and subtracting* the com- 
bined area of the holes cut for the tubes. Mul- 
tiply this by the leng-th of the boiler in inches and 
divide by 1728. This will g'ive the number of 
cubic feet of water in it. To chang-e to g-allons 
multiply by 7.5. To find weig-ht multiply the 
number of g-allons by 8.33. The steam space of a 
tubular boiler is found by ascertaining- the area of 
one of the heads above the water line, and mul- 
tiplying- it by the leng-th of the boiler in inches. 
Divide by 1728. If there is a dome the cubical con- 
tents must be added to the above. Por rules to 
determine areas of seg-ments of circles, see Chap- 
ter 48. 

When an eng-ineer says that his boiler "foams," 
it is g-enerally understood that he means that the 
water froths up into the steam space, so that it is 
almost impossible to tell where the true water 
level is. It is a dang-erous fault, and is usually 
caused by foul water or too small a steam space. 
Sometimes chang-ing- from salt to fresh water, or 
vice versa, will cause a boiler to foam. When we 
say that a boiler "primes," we usually mean that 
more or less water is continually carried oif with 
the steam, causing- it to be what is called "wet 
steam." When the report of an evaporative test 
is g-iven, it is unreliable unless the condition of 
the steam is known, for water carried off in this 
way is not evaporated, but when it is so counted, 
causes the boiler to be credited with g-reater 
efficiency than it is entitled to. 

If an uprig-ht boiler primes it may sometimes be 



90 MODERN EXAMINATIONS 

stopped by removing- some of the tubes, thus in- 
creasing* the steam space. If it is a tubular 
boiler, and the priming- is excessive it may be 
stopped by putting- in a dry pipe. Priming- is a 
source of loss of fuel, and may result in injury to 
the eng-ine. Nearly all boilers prime more or 
less, and it may g-o on undetected for years, unless 
the steam is tested, as the glass g'ages give no in- 
timation of it. 

Generally boilers furnishing steam for auto- 
matic engines prime less than if the engine is a 
throttling one, taking steam nearly whole stroke. 
A separator is a device forming a part of the 
steam pipe, and is applied for the purpose of 
catching the water in the steam, and preventing 
it from going to the engine. Water so entrapped 
may be returned to the boiler at a high tempera- 
ture. 



1 



OF STEAM ENGINEERS. 91 



CHAPTER XVIII. 

SAFETY VALVES. 

There are several rules relating* to safety valves 
which an eng-ineer who hopes to receive a first- 
class license should be familiar with, the first one 
that we shall call attention to being- the one, or 
rather several, for determining- the proper size of 
valve for any boiler. As we believe that the rule 
adopted by the United States Government is a 
very g-ood one, we shall speak of that first, and it 
says that we must allow one square inch of safety 
valve area for each two square feet of g-rate sur- 
face, in the case of a common lever valve, and 
allow one square inch of valve area to each three 
square feet of g-rate surface, if the pop valve is 
adopted. This refers to boilers using- natural 
draught, and for such it will be ample. 

We believe that the grate surface is the proper 
base for the calculation, rather than the heating- 
surface, for if the g-rate surface is large in pro- 
portion to the heating- surface, then if the size of 
valve was calculated from the latter, it might not 
be sufficient for the purpose intended, and become 
a danger valve instead of a safety valve. The 
English rule is to allow one-half square inch of valve 
area for each square foot of g-rate surface, which 
is identical with the above for natural draught and 
lever valve. Another one said to be Prof. Rank- 
ine's is to allow .006 of a square inch of valve area 
for each pound of water evaported per hour. 

It is rather a difficult manner to design a valve 



92 MODERN EXAMINATIONS 

by this rule, for who can tell how much water the 
boiler will evaporate in advance? 

We could g-ive what migfht be called "a shrewd 
guess," but that would not fill the bill. 

Another one, said to be the French rule, is as 
follows: Multiply the grate surface in square 
feet by the number 22.5. This g-ives number one. 
Add the number 8.62 to the steam pressure al- 
lowed. This g-ives number two. Divide one by 
two and the quotient will be the area of the valve 
in square inches. This rule embodies a correct 
principle, for it takes into account the steam 
pressure to be carried, which it may be well to 
do, for steam of a high pressure will escape into 
the atmosphere more rapidly than steam of a low 
pressure will, the openings being the same size, 
therefore we shall need a larger valve for a boiler 
that IS to carry a low pressure of steam. 

It may be well to note, however, that the rule is 
defective in that the first number given should be 
much larger than it is to give correct results. 

For illustration, suppose that we have a 54-inch 
boiler with a grate surface of 25 square feet, to 
carry 80 pounds steam pressure. Applying the 
rule, we have 25x22.5=562.5; 80+8.62=88.62; 
562.5^88.62 = 6.34 square inches valve area, which 
is just about one-half what it should be. 

A rule adopted by the German government 
takes into account the heating surface of boiler, 
and pressure to be carried, but as it is not com- 
plete without a table it will not be inserted here. 
If the candidate gives the first rule mentioned 
probably it will be all that will be required of him. 

We think that it is not generally understood 
that a valve having a bevelled seat will not give as 
large an opening as one having a level one will, 
and at first thought it will appear as if it would be 



OF STEAM ENGINEERS. 93 

the same in both cases, for although the valve and 
seat may be on an angie of say 45°, does not the 
valve lift just the same, thus bringing- all parts of 
it at the same distance from the seat as if there 
was no bevel to be taken into account? 

If any one who is interested will draw a sketch 
of a valve and seat on an ang-le and represent the 
valve as lifted one-quarter inch from its seat, they 
can easily see that the distances measured at 
rig-ht ang-les to the seat, between the valve and 
the seat, is less than one-quarter inch, and as this 
is what determines the area of an opening, it must 
of necessity be less than a flat valve and seat 
would give. To determine what the area of open- 
ing will be the following rule is given, provided 
the angle is at 45° : Multiply the diameter of the 
valve by the lift, and this product by 2.22. Mul- 
tiply the square of the lift by 1.11. Add the two 
products and their sum will be the required area 
of the opening of valve in square inches. 

The rule for determining the area of opening of 
any valve, with a bevelled seat, at whatever angle 
it may stand, provided, of course, that the lift of 
the valve is less than the depth of the seat, is as 
follows: Mtiltiply the diameter of the valve by 
the lift, and this product by the sine of the angle 
of inclination and this product by 3.1416. This 
gives what may be termed the first product. 
Multiply the square of the lift by the square of 
the sine of the angle of inclination, and multiply 
the- product so obtained by the co-sine of the 
angle of inclination, and this product by 3.1416. 
This gives what may be termed the second 
product. Add the first and second products to- 
gether and their sum will be the area of the open- 
ing in square inches. If both valve and seat were 
flat, then all that we should have to do would be 



94 MODERN EXAMINATIONS 

io multiply the circumference of the valve by its 
Lift and the product would be the area of the 
opening- in square inches. As these rules may not 
be fully understood by some, they will be illus- 
trated and fully explained in Chapter 19. 






OF STEAM ENGINEERS. 95 



CHAPTER XIX. 

MORE ABOUT SAFETY VALVES. — HOT AND COLD 
WATER PUMPS. 

Por the purpose of illustrating- the rules given 
in Chapter 18 for calculating- the area of safety 
valve opening's we shall g-ive one example, in order 
that the results may be compared. The author 
finds that in many works g-iving- these rules, dif- 
ferent examples are g-iven for each rule, but this 
is not at all necessary, and, in fact, is a detriment, 
for if two rules are g-iven for solving* the same 
problem the results should at least very nearly 
ag-ree. Let us take a valve four inches in diam- 
eter with a seat bevelled to an ang-le of 45°, and 
assume that the lift is one-fourth of an inch. 

Applving- the fi'rst rule w^e find that 4x.25x 
2.22=2^^22 which is our first product: .25x.25x 
1.11 = .069375, which is our second product. Add- 
ing- these two together we find that 2. 22+. 069375 
=2.289 square inches. It may be expressed in an 
abbreviated form as follows: DxLx2.22=A. 
L2 xl.ll=B. A+B=R, in which D=diameter of 
valve, L=lift of valve, A=first product, B = 
second product and R = area of opening-. Apply- 
ing- the second rule we find that 4x.25x.707x 
3.1416=2.2211, which is the first product; 707x 
707 X. 25 X. 25 X. 707x3.1416 = . 0693 which is our 
second product. When this product is written 
out in full it requires 17 decimal places to express 
it, but the result is not materially chang-ed by 
omitting 13 of them. 2.2211+.0693 =2-2904 square 



96 MODERN EXAMINATIONS 

inches area of opening'. It may be expressed as 
follows: D XL XSX 3.1416 = F. L^ x S^ x C X 
3.1416 = P. F+P=A, in which D= equals diam- 
eter of valve, L=lift of valve, S=sine of ang-le 
of inclination, C=co-sine of ang^le of inclination, 
F= first product, P= second product, A= area in 
square inches. If the valve and seat were flat, 
then we could make use of the third rule as fol- 
lows: 12.5664x25=3.1416 square inches. 

This rule may be expressed as follows: Cxiv 
= A, in which C= circumference, L=lift and A = 
area of opening* in square inches. We wish to 
call attention to the fact that the valve with a flat 
seat g^ives 37 per cent, more opening" than the 
one with a bevelled seat, at a 45-deg-ree ang-le, the 
lift being' the same in both cases, and as the ang^le 
decreases (from the perpendicular) the opening" 
g-rows less. 

The candidate should be familiar with rules for 
determining' the pressure at which a valve will 
blow off at under stated conditions; for telling* 
the leng-th of lever for a certain valve, and also 
the weig*ht required on a lever of g-iven leng"th to 
allow the valve to open at a stated pressure, and 
also should be ready to assume data for examples 
illustrating' all of these rules. 

He should also look up matters in connection 
with boiler feeders, and one of the inost difficult 
questions to g-ive a proper reply to, is how to de- 
termine the proper size of pump for a battery of 
boilers. Not that there is any lack of rules for 
this purppse, the most prominent one being- to 
provide a pump capable of delivering- one cubic 
foot or 7.5 g-allons of water per hour for each 15 
square feet of heating- surface. 

This is usually sufficient, and oftentimes larg-ely 
in excess of what will be used at any time. How- 



OF STEAM ENGINEERS. 97 

ever, it is well to have a pump large enough to do 
its work easily, for pumps should not be expected 
to run at the speeds given them in the maker's 
catalogue, as they are excessive. A good direct- 
acting pump will run at a very slow speed, and it is 
well to run it at from 25 to 50 strokes per minute, 
instead of from 100 to 300 as listed in some cata- 
logues. There is no way to tell in advance just 
how much water will be needed to operate a plant, 
but when the amount of coal consumed is known, 
then under average conditions the number of 
pounds of coal burned will be the number of gal- 
lons required. This of course, would not apply 
to plants that are used for heating purposes dur- 
ing the winter, and returning the water of con- 
densation by means of some trap, or other auto- 
matic arrangement, and for running an engine 
also, as the amount of water needed in the winter 
season is practically no more than what is needed 
in the summer time, although the amount of coal 
burned may be much greater. 

It is a very convenient way to refer to a pump 
manufacturer's catalogue when it is desired to 
know the capacity of a pump, but if it is desired it 
may be calculated by multiplying the diameter of 
water plunger by itself, and the product by .7854. 
By multipl5nng the product so obtained by the 
length of the stroke and dividing the product by 
231 the number of gallons per stroke may be 
known. The formula is as follows: 
AxL 

=G 

231 
in which A=area of piston, L= length of stroke 
in inches, and G= gallons contained. If a part of 
this space is occupied by a piston rod it must be 
dedncted from the above. If any form of injector 



98 MODERN EXAMINATIONS 

is to be used as a boiler feeder the capacity of it 
must be determined by experiment, or by consult- 
ing the manufacturer's catalogue. It ma}^ be well 
to remember that the capacity of an injector is 
much greater when the water is delivered to it 
under pressure than it is when it must lift its 
supply from a well or tank. 

A pump will take water much hotter than an in- 
jector (if the supply is above the pump,) because 
the steam supplying the injector must be con- 
densed and the water must be cold enough to do 
this. Hot water cannot be lifted as cold water 
can, because when the pump removes a part of the 
atmospheric pressure the partial vacuum is at 
once filled with vapor instead of a solid body of 
water. The only diiference between a hot water 
and a cold water pump is that if it is to be used 
for cold water only it is customary to make the 
valves of soft rubber, which answers every pur- 
pose; but if hot water is to be used, then the 
valves should be made of metal in order to insure 
durability. Sometimes hard rubber valves are 
used, but metal ones are better. 

It should be remembered that a larger pump 
will be required to pump hot water for a given 
plant, than for the same one if the water is to be 
cold when pumped. Theoretically, a pump that 
is perfect in every way should just raise a column 
of water 33.947 feet high at sea level, or rather it 
should create a perfect vacuum, and then the 
pressure of the atmosphere on the surface of the 
water outside of the pipe should force it up, but 
perfection is rarely obtained in worldly matters, 
and pumps are no exception to the general rule, 
therefore they should never be expected to ele- 
vate water more than 25 feet, and they will work 
better if it is even less than this. 



OF STEAM ENGINEERS. 99 



CHAPTER XX. 

HEATING THE FEED WATER. — PROPER SIZE OF 
CHIMNEY FOR A STEAM PLANT. 

Under ordinary conditions water cannot be 
heated above 212° by exhaust steam without back 
pressure on the eng*ine (above the atmospheric 
pressure). A good form of heater, properly pro- 
portioned for the work that it has to do, will heat 
the water nearly as hot as this in every-day prac- 
tice, and in some cases water is delivered at the 
boiling- point almost constantly. This saves re- 
pairs on the boilers, by avoiding- excessive con- 
traction caused by pumping- cold water into a hot 
boiler. This alone will be of enoug-h value to 
repay the cost of a heater several times over, and 
we cannot g-ive a rule for calculating- just what 
this saving- will be, but the per cent, saved bv 
utilizing- a portion of waste heat in the exhaust 
steam may be determined by subtracting- the tem- 
perature of the water as it enters the heater from 
its temperature as it leaves the heater, and divid- 
ing- the remainder by the total heat of the steam 
in the boiler. 

For an example, suppose that we have water en- 
tering- at 40° P., and leaving- at 212°, and are using* 
steam at 70 pounds pressure; 212—40 = 172 Steam 
at 70 pounds pressure contains a total heat of 
1210°; 172^1210 = . 14, or in other words the saving 
would be 14 per cent, on all of the fuel used over 
what it would be if the water were pumped in cold. 



100 MODERN EXAMINATIONS 

In the case of a sing"le boiler using* 1% tons of 
coal per day, the cost of which is $3.50 per ton, 
the total saving* on fuel for one year of 300 days 
would be 3.50xl.50x.l4x300 = $220. It is not 
surprising, therefore, to note the very large num- 
ber of heaters that are manufactured at the 
present time, and that the variety of styles offered 
is so very great. If a heater is not giving satis- 
factory results an improvement may be made by 
covering it with some non-conducting covering, 
but the best results cannot be obtained unless the 
heater is large enough to allow the water to pass 
through it at a very slow rate of speed, that it 
may have time to take up the heat before it is dis- 
charged. In testing the heat of feed water, a 
valve near the heater should be opened, and the 
water allowed to run on to the bulb of a ther- 
mometer. 

If the candidate is asked to tell the difference 
between forced and natural draught he should 
state that by natural draught is meant the circu- 
lation of air through an ordinary chimney, caused 
by the difference in the weight of air on the out- 
side and the air and gases on the inside. The 
latter being the lightest are forced upward by the 
weight of the former, hence the draught is called 
natural. 

If a fan blower or steam jet is used to force the 
air and g'ases up throug'h the chimney, the draught 
is said to be forced. If the gases, or rather the 
products of combustion which are in the chimney 
are very hot they will be very light, and if they 
are very light they will ascend quickly, or in 
other words, the draught will be very strong. 
Thus may we reason from cause to effect as far 
as the draught is concerned, but when we go a 
little farther we see at once that if these products 



OF STEAM ENGINEERS. 101 

of combustion are very hot, it means a loss of 
heat, which in turn means money thrown away. 

Now, if we close our ash-pit doors, and supply 
the air necessary for combustion by means of a 
pipe led into the ash pit, which, if supplied by a 
fan, and we regulate the discharg'e of air so that 
we can g"et just enoug-h to burn the required 
amount of coal or, in other woids, to keep up 
steam, it is plain that we can create a draught, 
and a strong* one, too, without depending- on hav- 
ing- a larg-e amount of heat g-o up the chimney to 
make it. To get the full advantage of this ar- 
rangement, we must have a large amount of heat- 
ing surface to absorb the heat. Prom this it will 
be seen that forced draught is more economical 
than natural draught is, provided all the condi- 
tions are right for it. 

The author does not wish to be quoted as being 
an advocate of using forced draught under the 
conditions sometimes found where it is used, for 
he is not. Such conditions are that the natural 
draught is used as long as it is sufficient to make 
steam enough to run with, and then the forced 
draught is substituted, simply because a stronger 
draught can be secured by so doing. We do not 
believe in running a plant in this way, as it is not 
economical in the use of fuel, and it also tends to 
wear out boilers much faster than when they are 
used under proper conditions. 

In designing chimneys it is a good idea to make 
the area equal to the combined area of the tubes 
discharging into it, plus 10 per cent, for a round 
chimney or 20 per cent, for a square one. The 
height of it will depend on the surroundings to a 
great extent. It should not be less than 80 feet, 
and if there are high buildings in close proximity 
to it, then it must be carried up higher. Some- 



102 MODERN EXAMINATIONS 

times the area of the chimney is determined by 
the amount of coal burned on the grates per 
hour, as follows: First determine the necessar\^ 
height of chimney. Then multiply the pounds of 
coal that it is desired to burn per hour by the 
constant whole number 15. Divide the product so 
obtained by the square root of the height of the 
the chimney. 

The quotient will be the area of the chimney in 
square inches. For illustration, suppose that we 
have decided to erect a chimney 120 feet high, and 
wash to burn 12 pounds of coal per hour per 
square foot of grate surface, our grate being six 
feet square: 6x6 = 36 square feet of grate; 36x12 
=432 pounds of coal per hour; 432x15=6480. 
The square root of 120 is 10.95, and 6480^10.95= 
591.7 square inches. 

By consulting a table we find that a circle 27.5 
inches in diameter contains 593.95 square inches, 
which is near enough for all practical purposes, 
therefore the diameter of our round chimney or 
stack should be 27.5 inches. Or 591.7-^.7854 = 
753.3 and the square root of 753.3 is 27.45, which 
gives us the diameter practically the same as 
before. 



OF STEAM ENGINEERS. 103 



CHAPTER XXI. 

DESCRIPTION OF THE SEVERAL PARTS OF AN IN- 
DICATOR DIAGRAM. 

In this connection, a general knowledge of the 
steam engine indicator, its construction, utility, 
use and care is essential. 

The applicant should be able to give readily a 
description of the principles on which it works, 
tell the names of the different parts of an indi- 
cator card, explain how defects in engines are de- 
tected by it, and give full instructions as to how 
to calculate the mean forward pressure from it, 
also the back pressure, and explain how to lay 
out the perfect expansion line, and estimate the 
water consumption from the card. 

The indicator consists of a small cylinder, in 
which there is a nicely fitted piston made so as to 
be steam tight without the use of packing rings of 
metal, and by means of suitable connections this 
piston operates a pencil, which draws the card on 
a piece of paper, and to the intelligent engineer 
this card tells just what is transpiring in the 
cylinder, so far as variations in the pressure are 
concerned, as plain as if they were written out by 
a typewriter. 

The indicator card does not tell us everything 
that we wish to know along this line, for in reality 
it is but a steamgage, telling us how much press- 
ure we have at all parts of the stroke, taking the 
line of perfect vacuum as a basis. Its principal 



104 MODERN EXAMINATIONS 

use is to tell whether the valves are set rig'ht or 
not, and to measure the power developed b}^ the 
eng"ine. If a small card is taken at one time and a 
larg-er one at some other time, the difference be- 
tween the two represents the difference in the 
load at the time w^hen they were taken, other con- 
ditions being- the same. 

The indicator is of necessity a delicate instru- 
ment, and as such needs to be well taken care of, 
for even slight defects in it lead to conclusions 
that are erroneous, sometimes seriously so. A 
full description of all of the parts of a card is not 
necessary here, but mention of them by way of a 
reminder may be of interest. 

The admission line shows how and when the 
steam is admitted, the steam line shows how the 
amount admitted compares with the amount re- 
quired to g-et best results, the expansion line 
helps to locate leaks, the line of exhaust opening* 
tells us when the exhaust valve releases the steam, 
the counter-pressure line tells us how much back 
pressure we have, and the compression line tells 
us when the exhaust valve closes. 

After a card consisting- of the above lines is 
taken, the steam is shut off, and another line 
drawn, which is called the atmospheric line. 
Prom this a perfect vacuum line is located by 
measuring- downward, using- the scale correspond- 
ing- to the spring- used in the instrument when the 
card w^as taken. In places that are near the sea 
coast or situated on low ground inland, it is cus- 
tomary to put it at 14.7 pounds below the atmos- 
pheric line, but the author received a letter a short 
time ag-o, from a friend, who lives where the 
atmospheric pressure is but 11.5 pounds, so that 
when a card is taken from his engine, the vacuum 
line must be drawn 3.2 pounds higher up than is 



OF STEAM ENGINEERS. 



105 



ordinarily done. We know of no inflexible rule 
for calculating- this pressure by the heig-ht, for 
the air g-rows lig-hter very fast as we ascend, and 




moreover, it is not always of the same density or 
weig-ht in the same place, the variations being' indi- 
cated bv the barometer and the thermometer. 



106 MODERN EXAMINATIONS 

Scientific observations made by a party travel- 
ing* to the Rocky Mountains show that at an eleva- 
tion of 6000 feet above sea level, the pressure was 
11.48 pounds; when a point a little more than 
14,000 feet high was reached it was 7.1 pounds. 

What we ordinarily call forward pressure of 
the steam on the piston is found as illustrated by 
Fig-. 1, in which S is the steam line of a card, E 
the expansion line, A the atmospheric line and V 
the line of perfect vacuum. Prom the point 1 
draw a line 3 to the atmospheric one, and at rig^ht 
ang-les to it. Prom the point 2 draw a similar 
one, 4. The space enclosed by 3 on the right, the 
steam and expansion lines on the top, 4 on the left 
and A on the bottom represent the forward press- 
ure as we usually speak of it. If we wish to ob- 
tain the absolute forward pressure the lines 3 and 
4 must be continued down to the vacuum line V, 
and this line then becomes the boundary on the 
bottom instead of the line A. 

What we usually call the back pressure on the 
piston is represented by the space enclosed by 
the line 3 on the right, and the counter pressure 
and compression lines C C on the top, the line 4 
on the left and the line A on the bottom. If we 
wish to obtain the absolute back pressure, we 
must take the line V as the boundary of the lower 
side of the space. The difference between the 
two, namely, the forward and the back pressure, 
is the mean effective pressure. There are at least 
three ways of finding the mean effective pressure 
from the card, and one of them is to divide the 
length of it into 10 parts, and ascertain the aver- 
age height of the upper line above the lower one, 
measured on the scale corresponding to the 
spring used in the indicator when the card was 
taken. 



OF STEAM ENGINEERS. 107 

. Another way is by using- the planimeter to trace 
over the card, and note the readings of the ver- 
nier. Then divide the number of the spring- used 
by the leng-th of the card, and mtiltiply the 
quotient by the reading- of the vernier. The 
product will be the mean effective pressure. 
Another way is to beg-in the tracing- with the 
planimeter, at some point at the right-hand side 
of the card, and g-oing- over it in the direction 
traveled by the hands of a watch, until the start- 
ing- point is reached. Then cause the tracer to 
travel in a perpendicular line until the vernier 
stands at zero or 0. The distance between the 
two points measured on the corresponding scale 
is the mean effective pressure. 



108 MODERN EXAMINATIONS 



CHAPTER XXII. 

RULES FOR LAYING OUT THE THEORETICAL EX- 
PANSION LINE. 

In Chapter 11 we promised to g-ive a rule for 
la^dng" out the theoretical expansion line, and now 
is a g-ood time to do it. 

Referring- to Fig. 2, which is an ordinary indi- 
cator card, we will first draw the vacuum line V at 
a point 14.7 pounds below the atmospheric line, 
and the clearance line B at a point far enough 
from the admission line to represent the percent- 
ag-e of clearance. We will now make a dot on the 
expansion line at D and from it draw a line parallel 
to the atmospheric line, represented by D P. 
Now draw another line from D at right angles to 
the atmospheric line, as at D G. 

. Next from the point P draw lines 1, 2, 3, 4, 5, 6 
and 7. Prom the points where these lines cross 
the line D P erect perpendicidar lines 0, 0, 0, 0, 
0, 0, and from the points 1, 2, 3, 4, 5, 6 and 7 draw 
horizontal lines. The points where these lines 
intersect are the points w^here the expansion line 
should be. 

Por cards where the point of cut-oif is short, a 
very convenient way of laying* out the expansion 
line may be found illustrated in Pig. 3, in which 
the vacuum line is drawn in its proper place as be- 
fore, and also the clearance line. Draw the first 
vertical line through the point of cut-off, and the 
others the same distance apart that this is from 



OF STEAM ENGINEERS. 



109 



the clearance line. Starting* from the point of 
cut-off draw lines to the base of the vertical lines 
as shown. Where the slanting lines intersect the 




vertical ones are the points through which the 

expansion line must pass, as shown in the figure. 

The rule that was given in Chapter 11 for de- 



110 



MODERN EXAMINATIONS 



termining the mean effective pressure when the 
initial pressure and point of cut-off are known is a 
g-ood one, and this rule it may be remembered 




g-ave us a mean effective peessure of 41.788 pounds 
under stated conditions, but wishing- to demon- 
strate the matter to our own satisfaction we con- 



OF STEAM ENGINEERS. Ill 

structed a theoretically perfect card, but without 
the clearance line for convenience, assuming- the 
spring- to be 40. "We then carefully measured off 
the ordinates, and obtaining- the mean effective 
pressure from them found it to be 42 pounds. 

We then went over it with a planimeter and 
found the reading- of the vernier to be 5.16. The 
length of the card is five inches; 40^5x5.16=41.28 
pounds. Going- over it again with a planimeter 
and after returning- to our starting- point, travel- 
ing- in a vartical line until the vernier stood at 
zero, and measuring- the distance between the two 
points, we found that the mean effective pressure 
was 41.5 pounds, and so we believe that the rule 
which calculated it to be 41.788 was correct. 

It is quite possible that cards may be furnished 
the candidate for a license which were taken from 
engines whose valves were improperly set, and he 
may be required to tell what the trouble was with 
them, and what the remedy is. 

Among- other thing-s that are shown by the 
card, we are told that from it we can calculate the 
amount of water used by the eng-ine in developing- 
power. This calculation is founded principally 
on the fact that if we know what the pressure of 
the steam is at the end of the stroke, we can 
ascertain what its weig-ht is from tables published 
for that purpose. As a pound of water evapo- 
rated into steam will still weig-h a pound, if we 
know the weig-ht of the steam it is ail easy matter 
to calculate how much water it took to make that 
steam. But after we have made all our calculation 
along this line the question naturally arises as to 
whether this will account for all of the water 
or not. 

A moment's reflection will convince us that it 
does not Suppose that 10 per cent, of the steam 



112 MODERN EXAMINATIONS 

is condensed upon being- admitted to the cylinder. 
What then? The amount so lost is immediately 
replaced by more steam from the boiler, the 
pressure is created and maintained, and as the 
indicator is simply a steam g'ag-e, it can g'ive no in- 
timation of the loss of steam, or rather of water, 
from this cause. There is also a loss from radia- 
tion and other causes, so that when the water con- 
sumption is calculated from the card, and then a 
comparison made with the amount actually 
pumped into the boilers and they do not ag-ree, 
there is always some one ready to decry ^'theory " 
and claim that practice alone is of value. 

Where the water consumption is calculated 
from the card, it is not always proper to take the 
actual terminal pressure as showing- the amount of 
steam used, for the exhaust valve may open before 
the piston reaches the end of its stroke, and so 
cause the pressure to fall much more rapidly than 
it would were the fall due to expansion alone. 
Prom this it will be seen that the expansion line 
should be continued to the end of the stroke, and 
the terminal pressure measured from it, or 
usually it will be all right to take the pressure at 
the point of release, as the difference will be very 
small. Care should be taken to measure this 
pressure from the line of perfect vacuum. The 
water consumption may also be calculated from 
the pressure at the point of cut-off. Rules will be 
ofiven and explained at length in succeeding" 
chapters. 



OF STEAM ENGINEERS. 113 



CHAPTER XXIII. 

CALCULATING THE WATER CONSUMPTION OF AN 
ENGINE FROM AN INDICATOR DIAGRAM. 

Our first move in explaining- the rule or rules 
for calculating- the water consumption by the 
card, or the water accounted for by the indicator, 
will be to draw the card Fig. 4. We have drawn 
it full size, in order that it may be the more 
readily understood. We believe that this card 
was taken from an engine whose cylinder is 24 
inches in diameter, and the stroke is 48 inches, 
and the speed is 65 revolutions per minute. There 
was a No. 40 spring- in the indicator when it was 
taken. The point 2 is the point of cut-off, 3 is 
the point of release, 5 the point of compression, 
V the vacuum line, and 1 and 4 are lines drawn for 
Convenience in making- measurements. 

A few moments consideration will show that 
the pressure of the steam, taken for the purpose 
of calculating- the water consumption, must be 
reckoned from that existing- at the point of re- 
lease 3, or perhaps, more properly speaking-, what 
the pressure would be if the expansion line were 
extended until it intersected the dotted line 4, 
which means the end of the card. It will answer 
every purpose in a majority of cases to take it at 
point of release, as the difference will be unap- 
preciable. 

We repeat, then, that it is proper to take the 
pressure at the point of release, for it makes no 



114 



MODERN EXAMINATIONS 



difference what the initial pressure is, or where 
the point of cut-off is located, or how much steam 
was admitted after the cut-off valve closed, for the 




pressure existing* after all of these operations 
have taken place is that which indicates the 
weight of the steam, and from this we must 



. 



OF STEAM ENGINEERS. 115 

decide the amount of water required. In this 
case the absolute pressure at 3 is 27 pounds. 
Referring- to *'A Manuel of Rules, Tables and 
Data for Mechanical Engineers, "by D. K. Clark, we 
find that one cubic foot of this steam weig-hs .0673 
pounds. We must now ascertain how many cubic 
feet of steam at this pressure we are using* per 
hour, and we shall be able to tell how much the 
whole of it weig-hs, and the number of pounds ac- 
counted for, per horse power. 

Prom this it may be seen that the cubical contents 
of the cylinder must be ascertained, but the space 
occupied by the piston rod will not be taken out, 
as it will affect the result but very little. The 
area of a 24-inch circle is 452.39 square inches. 
The stroke is 48 inches; 452.39x48=21,714.72 
cubic inches, which is the volume of the cylinder 
reckoned by the stroke, but asthe clearance must 
be filled with steam at each stroke it must be taken 
into account. It is stated at four per cent. 21,- 
714.72 X. 04=868.58, and 21,714.72+868.58=22,583.3 
cubic inches for each stroke. As the eng-ine runs 
65 revolutions each minute, this space must be 
filled with steam 130 times during- each 60 seconds ; 
22,583.3X130=2,935,829 cubic inches, and by divid- 
ing this number by 1728 we have 1699 cubic feet of 
steam used per minute. As one cubic foot weig-hs 
.0673 pound we multiply ag-ain and 1699 X. 0673= 
114.3427 pounds per minute. As we wish to know 
the amount per hour we multiply by 60 and our 
product is 6860.56 pounds per hour. This then is 
the total amount of water accounted for by the 
indicator, according- to this mode of calculating- it. 
Our next move is to determine the horse power 
developed. 

The horse power constant is 7.13, and the mean 
effective pressure is 52.4, therefore 7.13x52.4= 



116 MODERN EXAMINATIONS 

373.6-horse power. Dividing* the total weight of 
the w^ater accounted for by the horse power devel- 
oped we have 6860.56-^373.6= 18.35 pounds of water 
per horse power per hour. This it wnll be noted 
is a very fair performance for a non-condensing 
engine. To some engineers this calculation may 
seem to be a very elaborate one, requiring many 
figures to put it in the proper form for inspec- 
tion, and it is hoped that the matter has been 
made plain step by step as it has progressed, and 
while no one can be expected to carry all these 
figures in his head, and draw them out to order 
when wanted, still if any one who is not thor- 
oughly familiar with the manner of solving such 
problems will study out the principle involved it 
will make what appeared to be a hard lesson to 
start wnth an easy one at the finish, and such cal- 
culations have an attraction for the engineer who 
is thoroughly interested in his business, as they 
tend to relieve the monotony of the ceaseless 
routine of w^ork in the engine and boiler-room, 
and furthermore the author will say, while speak- 
ing for himself, that these matters possess a fas- 
cination which is equalled by few others and 
excelled by none. But to return to the subject. 
However lengthy the above calculation may seem 
it is incomplete, as it does not take into consider- 
ation all of the factors which form a part of the 
complete whole. It will answer for all practical 
purposes, and is by no means to be despised, but 
a formula will now be referred to which embraces 
every point that can effect results, a most 
thorough and complete rule, and in fact, it may be 
termed a masterpiece. 



OF STEAM ENGINEERS. 117 



CHAPTER XXIV. 

MORE ABOUT CALCULATING THE WATER CONSUMP- 
TION OF AN ENGINE. 

We will first give the formula as we find it for 
determining- the water accounted for per horse 
power per hour at the point of release. This 
formula is said to be used in the Massachusetts 
Institute of Technology: 

13750 

(R+E Wr)— (H+E Wh)= 



M.E.P. 

number of pounds of steam accounted for at re- 
lease, in which, together with another formula 
using pressure at point of cut-oif, the following 
symbols are made use of : ME P= mean effective 
pressure; C=portion of stroke completed at cut- 
off expressed in decimals; E=per cent, of clear- 
ance or the volume of clearance compared with 
the volume of the cylinder; R= proportion 
of stroke completed at release; H=propor- 
tion of stroke uncompleted at compression; 
Wc= weight of one cubic foot of steam at 
cut-off pressure; Wh=weight of one cubic foot of 
steam at compression pressure; Wr= weight of 
one cubic foot of steam at release pressure. 

An explanation of this formula is as follows: 
The constant whole number 13,750 is to be divided 
by the mean effective pressure, and the quotient 
so obtained we will set down by itself, calling it 
our first answer. To R we must add E, and mul- 



118 MODERN EXAMINATIONS 

tiply their sum by Wr, and the product so ob- 
tained we will call our second answer. To H we 
must now add E, and multiply their sum by Wh, 
and this product we will call our third answer for 
convenience. Subtract the third from the second 
and multiply the remainder by the first. The 
product will be the pounds of water per horse 
power, per hour, at release pressure. 

We will now work out an example by this 
formula, taking- for illustration the card shown 
in Fig-. 4, Chapter 23, and when we substitute for 
the symbols their values taken from this card, our 
formula is as follows: 

13750 

f .%4+.04 X .0673)— (.071+.04 x .0411)= 16 53 

52.4 
pounds of water per horse power per hour. 
This is somewhat less than the result ob- 
tained by a former rule, but from the conditions 
stated it is only reasonable to suppose that it 
would be from the start, for the simple reason 
that while the first rule given counts all the steam 
lost, when it is released by the exhaust valves, 
this rule takes into account the fact that a portion 
of it is saved by the closing- of the exhaust valve 
before the completion of the return stroke, in 
other words by compression. 

In order to avoid any misunderstanding- on the 
part of those who are not familiar with such com- 
putations as these, we shall now offer a full ex- 
planation of the way in which the figures were ob- 
tained. The total leng-th of the card is 5.25 
inches, and by measuring- from the end of the 
card to the point 3, we find that 27-28ths of the 
stroke has been completed when the exhaust valve 
opens, and reducing* it to a decimal fraction, we 
have .964. That is how we obtained R. The 



OF STEAM ENGINEERS. 119 

clearance is estimated at 4 per cent, of the volume 
of *.the cylinder, judging- by the distance from the 
piston to cylinder head when on the centre, plus 
the volume of the ports, etc. Thus we obtained 
E. Wr was obtained from a table in the manual 
referred to previously by D. K. Clark. By meas- 
uring" from the point 5 to the end of the card, we 
find it to be three-eig-hths of an inch, or one-four- 
teenth of the whole stroke. 1-14= .071. In this 
way we obtained H. Wh was obtained from 
Clark's manual. If it is desired to obtain the 
water accounted for by the indicator at the point 
of cut-off, the following- formula should be used: 

13750 

(C+E W6-)— (H+E W^)= 



M.E.P. 
pounds of water per horse power per hour. 
When we substitute for the symbols their values 
as determined by the card Pig-. 4, we have the fol- 
lowing-: 

13750 

(.25+.04 X .2586;— (.071+.04 x .0411)= 18.48 



52.4 
pounds per horse power per hour at the point 
of cut-off. 

The process is as follows: 13750^52.4=262.4, 
which is our first answer. . 25+. 04 X. 2586= 
.074994, which is our second answer. .071+.04X 
.0411= .004562. .074994— .004562 X 262.4= 18.48 
pounds. In this case the author has pursued his 
usual policy of illustrating- several rules g-iven, 
by using- the same data for all. 

It is a policy not always looked on with favor, 
as it shows up the difference too well, but as we 
are seeking- after knowledg-e, and as this book is 
written for the purpose of imparting* the same, it 
is better to look at these matters in their true 



120 MODERN EXAMINATIONS 

lig-ht. When two or more rules are g-iven by g-ood 
authority it is often a difficult task to decide 
which one is correct, but if the candidate is well 
versed in his favorite, and can explain it in detail, 
probably no inspector would refuse him a license 
on account of small differences in the results ob- 
tained. Some further comparison will be made in 
the next chapter. 



OF STEAM ENGINEERS. 121 



CHAPTER XXV. 

STILL MORE ABOUT CALCULATING THE WATER 
CONSUMPTION. 

The following- formula may be used for calcu- 
lating- the water accounted for at the point of cut- 
off: 

vs w 
=p 

H. P. 

In which V=volume of cylinder up to point of 
cut-off in cubic feet, S= number of strokes per 
hour, W=weig-ht of one cubic foot at cut-off 
pressure (absolute), H. P. = the horse power de- 
veloped, and P=the pounds of water per horse 
power. 

Assuming- the elements of the preceding- case, 
and again referring- to Pig*. 4, Chapter 23, we find 
that the area of the cylinder is 452.39 square 
inches. The cut-off takes place at 12 inches, and 
452.39 Xl2yl728= 3.14 cubic feet. The speed is 
65 revolutions per minute, or 7800 strokes per 
hour. The pressure at cut-off is 113 pounds, and 
the weig-ht of one cubic foot is .2586 pound. It 
was developing- 373.6 horse power. 

Then 3. 14 X 7800 X. 2586 ^373. 6= 16.95 pounds 
per horse power per hour. 

It will be noticed that w^e have not taken the 
clearance into account so far, for the reason that 
we wish to raise the question as to whether it 
should be a factor in the calculation, inasmuch as 



122 MODERN EXAMINATIONS 

it is filled by compressing- the exhaust steam. As 
it is generally conceded that the amount of clear- 
ance in the cylinder will effect the economy of the 
machine, and some authorities at least deem it 
proper to recog-nize it when making* calculations, 
we should like to present another question con- 
cerning* it. In this case it is four per cent., that 
is, it possesses .04- of the volume of the whole 
cylinder, but if we are using* the volume of it up 
to the point of cut-off only, is it proper to call it 
the same? As we have reduced the entire volume 
under consideration to one fourth of what it was, 
and have not reduced the volume of the clearance, 
is it not proper to say that the percentage is four 
times as much, or 16 per cent? 

Viewing it in this light then we have 16.95 
pounds per hour ; adding 16 per cent to it makes it 
19.66 per horse power per hour. Putting the re- 
sults of the four rules together we have for the 
1st rule, taking pressure at release, 18.36 pounds 
2d " " *' *' " 16.53 

3d " " *' " cut-off 18.48 

4th " " " " " 19.66 

Of course rules No. 1 and 2 should be classed to- 
gether, as the conditions are the same, and the 
difference in the results are not so large as they 
at first appear to be, for it is but 82 gallons per 
hour, even for this large engine, or less than 22 
gallons for each 100 horse power developed. 
Rules No. 3 and 4 may be compared, and the dif- 
ference between the results is but 53 gallons per 
hour, or less than 15 gallons for each 100 horse 
power developed. 

In the rules No. 2 and 3 it will be noted that 
the water consumption is calculated directly from 
the card, without bringing the size of the cylinder 
into the calculation at all. This can be done 



OF STEAM ENGINEERS. 



123 



where the rate onh^ is required, as in this case, 
and shortens up the process materially. 

We wish to emphasize this, for the answer so 




obtained is the amount of water accounted for per 
one horse power per hour, and if the whole 
amount accounted for is desired (when employing- 



124 MODERN EXAMINATIONS 

rulCvS 2 and 3), it must be multiplied by the power 
developed. In this book it has been one of the 
objects of the author to dispense with the use of 
tables as far as possible, but there is one which 
makes the calculation of the amount of water ac- 
counted for by the indicator such a simple matter 
that it is worthy of notice. 

This table w^as originally prepared by Mr. E. 
W. Thompson for the American Machinist, and in 
its orig-inal form is very full and complete, em- 
bracing* the terminal pressures from three to 60 
pounds absolute, both included, advancing by 
tenths of a pound, but for all practical purposes 
the whole and half pounds are sufficient. To use 
the table, first ascertain the absolute terminal 
pressure and take the number opposite to it in the 
table, which is to be divided by the mean effective 
pressure. The quotient so obtained w^ll be the 
pounds of dry steam accounted for per horse 
power per hour. For the purpose of illustrating 
the utility of this table, let us refer to Pig. 5, 
which is a reproduction of a card shown in Pig. 4. 
The pressure at the point of release is 27 pounds 
absolute. The number in the table which is op- 
posite 27 is 927.990. The mean effective pressure 
of this card is 52.4 pounds; 927.990--- 52.4= 17.71 
pounds dry steam per horse power per hour, or 
in other words, w^ater accounted for by the indi- 
cator. 

This as it stands is uncorrected for clearance 
and compression. If it is desired to do this, draw 
the dotted line, 6, in the figure, through the point 
of release parallel to the atmospheric line, and 
also the two vertical lines representing the ex- 
treme ends of the card. Ascertain the distance 
from the end of the card at the left to the place 
where the dotted line crosses the compression 



OF STEAM ENGINEERS. 



125 



line at 7. Multiply the pounds of water already 
accounted for by this distance in inches, and 
divide the product by the distance between the 
two vertical dotted lines. The quotient will be 




the water accounted for per horse power per 
hour, corrected for clearance and compression. 
Applying- the above we find that 17.71x5.1875 = 
91.8706, and dividing" this by 5.25, we find our 



126 



MODERN EXAMINATIONS 



quotient is 17.50 pounds. In many cases found in 
practice, however, the conditions will be some- 
what different than with this card, an illustration 
of them being- shown in Fig-. 6. In this case the 
terminal exceeds the compression pressure (both 
being- absolute); therefore it will be necessary to 
extend the compression line as shown and pro- 
ceed as before. 

The data in this case is as follows : Release 
pressure 28 pounds; number opposite 28 in 
table is 960.120, and the mean effective pressure is 
19 pounds; 960.120^19=50.53 pounds per horse 
power per hour. To correet for clearance and 
compression: The distance from the end of 
card at 8 to where the dotted line crosses the 
compression line is 3}i or 3.875 inches, and from 
the same point to other end of card is 3 11- 
16 or 3.6875 inches; 50.53x3.875=195.8037 and 
dividing- this Ly 3.6875 g-ives us a quotient of 53.1 
pounds per horse power per hour. It will be 
noted that this amount exceeds that obtained at 
first, which is what mig-ht be expected, as the 
compression is less than the terminal pressure. 



T. P. Number. 



T. P. 



117-300 3-5 

153-880 4.5 

189-750 5-5 

225. 240 6.5 

260.540 7.5 

295-440 8.5 

330.030 9.5 

364-400 10.5 

398.640 II. 5 

432.720 12.5 

466.570 13.5 

500. 220 14.5 

533-850.. 15-5 



Number. 

135-748 

171-945 
207.598 
242.970 
278.063 
312.800 

347.273 
381.570 

4T5.725 
449.688 

483.435 
517.070 
550.638 



OF STEAM ENGINEERS. 

T. P. Number. T. 

567-360 16 

600.780 17 

633960 18 

666. 900 19 

699.800 20 

732.690 21 

765-380 22 

798. 100 23 

830.640 24 

863.250 25 

895.700 26 

927.990 27 

960. 120 28 

992.380 29 

1024. 500 30 

1056.480 31 

1088.320 32 

1120.350 , S3 

1152-260 34 

1184.050 35 

1215.720 36 

1247.640 37 

1279.460 38 

1311-180 39 

1342. 800 40 

1374-320 41 

1405.740 42 

1437-060 43 

1468. 720 44 

1500.300 45 

1531-800 46 

1563-220 47 

1594-560 48 

1625.820 49 

1657.000 50 

1688. 100 51 

1719. 120 52 

1750-060 53 

1780.920 54 







127 


P. Number. 


.5. .. 


584.100 


•5 




. 617.400 


■5 




. 650.460 


•5 




• 683.378 


•5 




. 716.270 


•5 




. 749.060 


•5 




• 781.763 


•5 




. 814.393 


•5 




. 846 965 


•5 




• 879.495 


•5 




. 911.865 


•5 




• 944-075 


-5 




. 976.268 


•5 




. 1008.458 


•5 




. 1040.508 


-5 




. 1072.418 


•5 




• 1104.350 


•5 




. T136.420 


•5 




. 1168.170 


•5 




. 1199.900 


•5 




. 1231.693 


-5 




- 1263.563 


■5 




• 1295.333 


•5 




. 1327.003 


•5 




• 1358-573 


•5 




. 1390.043 


•5 




• 1421.413 


•5 




. 1452.900 


-5 




. 1484.520 


•5 




. 1516.060 


•5 




- 1547-520 


-5 




. 1578.900 


•5 




. 1610.200 


•5 




. 1641.420 


5- 




. 1672.560 


•5 




. 1703.620 


5- 




. 1734.600 


•5- 




. 1765.500 


•5- 




. 1796.320 



128 



MODERN EXAMINATIONS 



T. P. Number. T. P 

55 1811.700 55.5 

56 1842.960 56.5 

57 1874.160 57.5 

58 1905-300 58.5 

59 1936.380 59.5 

60. . . . 1967.400 60.5 



Number. 

1827.338 
1858.568 
1889.738 
1920,848 
1951.898 
1983.888 



OF STEAM ENGINEERS. 129 



CHAPTER XXVI. 

CONCLUSION OF THE SUBJECT OF WATER CON- 
SUMPTION. 

There is still another style of card to which we 
wish to apply the rule, which makes use of a table, 
an illustration being- shown in Pig". 7. In this case 
the cut-off is very short, and as a consequence the 
terminal, or, more properly speaking, the release 
pressure, is below the atmosphere. This makes 
no difference, so far as determining- the water ac- 
counted for is concerned, but inasmuch as it may 
prove a stumbling'-block to some reader, we have 
deemed it best to introduce it at this point. 
Where the steam is expanded below^ the pressure 
of the atmosphere, and the exhaust valve is opened 
before the end of the stroke, the pressure rises 
instead of falling-, or, in other words, is just the 
reverse of what takes place w^hen the release 
pressure is above the atmosphere, therefore, the 
rule which tells us to continue the expansion line 
to the end of the card, carr^dng- it out in the same 
manner that it would have been carried out, pro- 
vided the exhaust valve had not opened before the 
completion of the stroke, applies to this case as 
well as to others which have been illustrated. As 
the release and terminal pressure are so much be- 
low the compression, we must continue the com- 
pression line downward as shown at 9 in the 
fig-ure. Applying- the rule w^e find that the termin- 
al pressure is 10.5 pounds absolute. The number 



130 



MODERN EXAMINATIONS 



Opposite 10.5 in the table is 381.57. The mean 
effective pressure is 10.25 pounds; 381. 57 -=-10. 25 = 
37.22 pounds of water accounted for per horse 




power per hour uncorrected for clearance and 
compression. 

The distance from the end of the diagram at the 



OF STEAM ENGINEERS. 131 

left to the point where the two lines cross at 10 is 
3.875 inches, and the total leng-th of the card is 
4.25 inches; 37.22x3.875^4.25=33.93 pounds cor- 
rected for clearance and compression. The en- 
gine from which this card was taken is one of the 
best made, and its builder has a world-wide repu- 
tation as a builder of first class machines, and yet 
the water rate is hig-h, and its efficiency low ac- 
cordingly, but what is the cause of it? Simply 
because it is underloaded. Suppose that more 
machinery should be put into the factory which is 
run by this engine until the terminal pressure 
would be 25 pounds instead of 10.5 pounds as at 
present. Then the water consumption would be 
reduced to about 20 pounds, although no change 
had been made in the engine. This shows the loss 
due to running an underloaded engine, but at the 
same time the machines in that factory are all 
running up to full speed, which could not be said 
if the engine had a heavy load to carry, for there 
would be times when the speed would be reduced, 
causing the output to be lessened, which would be 
a greater loss than is caused by what fuel is wasted 
under the present conditions, and this is a leak 
that cannot be detected by the indicator. 

Concerning a rule for calculating the water rate 
in the case of a compound engine, would say that 
we know of no better one than rule No. 1 as al- 
ready given for a simple engine, but in using it 
the high-pressure card should be made use of, and 
care taken to divide the total amount of water ac- 
counted for by the total power developed in both 
cylinders. 

The first rule mentioned, in w^hich the table 
given in Chapter 25 is used, may be applied to the 
case of a compound engine, using the diagram 



132 MODERN EXAMINATIONS 

from the low pressure cylinder for the calcu- 
lation. 

These rules are useful for the purpose of 
making" comparisons of different engines, and 
also of the performance for the same eng-ine 
under varying conditions. 



OF STEAM ENGINEERS. 133 



CHAPTER XXVII. 

CAUSES FOR DEFECTIVE INDICATOR DIAGRAMS. 

While the indicator points out many defects in 
valve setting-, and also in the construction of the 
steam engine, still when a card is taken and found to 
be imperfect, it is not wise to "jump to a conclu- 
sion" as to the cause of the trouble, as there may 
be more than one cause for it. Take for instance, 
the case of a card or diagram that shows a higher 
terminal pressure than should be according to the 
ways of laying out the theoretical expansion line 
illustrated in Chapter 22. We would naturally 
conclude that the steam valve leaked, thus admit- 
ting more steam after the cut-off had taken place, 
and raising the expansion line accordingly, but 
such a conclusion might be an erroneous one, as 
the defect may be due to re-evaporation, that is, 
there may be water in the steam w^hen first ad- 
mitted to the cylinder, or it may be due to initial 
cylinder condensation, by which we mean that the 
cylinder walls may have been cooled down by a 
low terminal pressure during the previous stroke, 
so that when steam is again admitted, although it 
may have been dry, still the effect of this lower 
temperature is to cause some of the incoming 
steam to be condensed at once, but after the cut- 
off has taken place and the pressure grows less as 
the piston advances, this water of condensation is 
again evaporated by the heat present, and hence 
the expansion line is raised. 



134 MODERN EXAMINATIONS 

Again, it is often inconvent to ascertain the 
exact clearance, so that the best that we can do is 
to approximate it, and if it is really more than we 
have calculated on, then the actual expansion line 
will be above the theoretical one, althoug-h no 
steam has been admitted since the cut-off took 
place. On the contrary, if the actual is below the 
theoretical expansion line, it may be due to the 
fact that, in estimating- the volume of the clear- 
ance, an error has been made in calling* it more 
than it really is, so that the only cause for differ- 
ence betw^een the. two lines is this error in the be- 
g-inning" of the process. However, if the engineer 
is satisfied that no error exists here, the fall in 
the expansion line points to a leak in the piston, 
for, as it is pushed forward, some of the steam 
passes by it, over into the other part of the cylin- 
der hence the undue fall in pressure. Or it may be 
that the exhaust valve leaks, thus allowing* some 
of the steam to pass out to the exhaust pipe with- 
out doing- its share of the work. 

There is at least one other reason for this fall 
in the line which will only apply to extreme 
cases, and that is excessive condensation, after a 
cut-off has taken place. If an eng-ine is located in 
a very cold place, without suitable protection by 
lag-g-ing- or covering* with some non-conductor, and 
the weather is cold, then the condensation is 
g-reat, and will cause the line to fall when no 
defect exists in the eng-ine itself. If the line falls 
in a proper manner for a time and then suddenly 
rises, it shows that the steam valve is reopened, 
thus admitting- another charg-e of steam, before 
the completion of the stroke. In the case of 
some eng-ines it is not such an easy matter to lo- 
cate the cause of such distortion as mig-ht be sup- 
posed. A certain engine having valves which are 



OF STEAM ENGINEERS. 135 

actuated in a similar manner to the Corliss valve, 
was found to be in a bad condition. A diagram 
taken from it showed that the steam valve re- 
opened at about five-eighths of the stroke. An 
examination of the eccentric showed that it was 
in its proper place. On the hub of the jim-cranks 
which operated the steam valve was a mark which 
corresponded to a similar mark on a collar located 
on a sleeve which formed a bearing- for the valve 
stem. With the engine on the centre, these 
marks were found to be in such a position as to 
form one continuous line, thus showing that the 
valve w^as properly set. Still, when another 
diagram was taken, it was very plain that the 
valve reopened as before. When the bonnet on 
the other side of the cylinder was taken off to 
compare the marks on valve and cylinder, it was 
found that they did not agree, thus showing 
plainly that the valve was not properly set, and 
at the same time pointing out the fact that it was 
due to a twist in the valve stem. 

If the expansion line falls very suddenly at say 
three-quarters stroke, it indicates that the ex- 
haust valve opens sooner than than it ought to. 
If the counter-pressure line rises suddenly before 
it is time for compression to begin, it indicates 
that the exhaust valve is closed sooner than it 
ought to be, and if the compression exceeds the 
initial pressure, it also shows that the exhaust 
valve closes too soon, and this is not only a 
wasteful condition of affairs, but a dangerous one 
as well. It is wasteful because it causes the point 
of cut-off to be lengthened to run the same amount 
of machinery, causing a direct waste to that ex- 
tent, and it is dangerous because it brings a 
greater pressure to bear on the cylinder head 
than has been calculated on in some cases, and 



136 MODERN EXAMINATIONS 

also because if there should be water carried over 
for any cause, and the cylinder is not perfectly 
drained during* the return stroke, there is more 
reason to believe that the effect will be disastrous 
than if the compression is light, under normal 
conditions. No inflexible rule can be given for 
the amount of compression that will give best 
results, but it is only reasonable to assume that 
the greater the speed the greater will be the com- 
pression advisable, other conditions being equal. 



OF STEAM ENGINEERS. 137 



CHAPTER XXVIII. 

POWER DEVELOPED BY DIRECT STEAM AND BY 
EXPANSION. 

The indicator diagram enables us to tell, in ad- 
dition to other things, how much of the work 
done is furnished by steam direct from the boiler, 
and how much is furnished by the expansion of 
this steam. 

Suppose that we take an indicator card in which 
the admission line is at the left hand and the ex- 
pansion line at the right hand. We will draw a 
perpendicular line from the point of cut-off down 
to the line of perfect vacuum. Now all of the 
space at the left of our perpendicular line between 
the steam line and the vacuum line represents the 
work by direct steam pressure, and all of the 
space at the right of the perpendicular line be- 
tween the expansion line and the vacuum line 
represents the work done by the expansion of the 
steam. 

It has been claimed that when we take into ac- 
count the work done by direct steam pressure we 
should stop there, as that is all that there is to it, 
and that to figure in the expansion of the steam is 
to claim to get double duty out of it, but we do 
not see how it is possible for this claim to be 
made good, for when the steam is cut off in the 
cylinder it is not all used up at once, for the force 
in it at the point of cut-off has been supplied di- 
rectlv from the boiler, as none of the benefits of 



138 MODERN EXAMINATIONS 

the expansive qualities of it have been made use 
of, so far as performing* work in the cylinder is 
concerned, and if it were immediately exhausted 
at this point there is no doubt that it would re- 
quire more coal to devolop 100-horse power than 
it does at present. 

The proportion of the work done during- ex- 
pansion, to that done during- the time that the 
steam is admitted to the cylinder up to the point 
of cut-off, is represented by the hyperbolic log-ar- 
ithm of the ratio of expansion. Suppose that the 
ratio of expansion is four, the hyperbolic log-ar- 
ithm of which is 1.3863. Then if we call the 
amount of work done previous to cut-off unity, or 
in other words call it one, then the work done 
during- expansion will be 1.3863, hence the rule. 
To find the work done during- expansion, multiply 
the hyperbolic logarithm of the ratio of expansion 
by the work done during- the period of full steam. 
The product will be the work done during- expan- 
sion. The words "power developed " may be in- 
serted instead of the words "work done," if so 
desired, for althoug-h the terms are not inter- 
changeable as a rule, still it must be remembered 
that this is an example in proportion only. 

It should not be forgotten that such rules do 
not always take account of clearance or compres- 
sion, and that the pressures are all absolute, as is 
always the case when the full power developed by 
the engine is to be calculated. 

To demonstrate the correctness of this rule 
may seem to be a complicated operation to some 
engineers, but in reality it is a very simple one. 
It may be done as follows : 

Draw a theoretically perfect card, v/ithout clear- 
ance or compression, putting the cut-off at one- 
quarter stroke, making the initial pressure 80 



OF STEAM ENGINEERS. 139 

pounds above the atmosphere, or 95 pounds abso- 
lute. Now draw a perpendicular line from the 
point of cut-of to the vacuum line. Having* done 
this, the author took a planimeter and carefully 
measured the area of the space representing- the 
work done prior to the cut-off point and found it 
to be 2.96 square inches. Now, as the cut-off took 
place at one-quarter stroke, the ratio of expansion 
is 4, the hyperbolic logarithm of which is 1.3863. 
By multiplying- 2.96 by 1.3863, we find that the 
product is 4.10, which should be the area of the 
space representing" the work done by expansion. 
As the actual reading- of the plainimeter was 4.14, 
it proves that the rule is correct, for we do not 
expect that these reading's will always agree ex- 
actly, and a difference of .04 in a case like this is 
not of enough importance to be taken into ac- 
count. 

Some writers tell us that if w^e are running* an 
automatic engine, we should carry such a press- 
ure on our boilers that the steam in the cylinder 
will expand down to atmospheric pressure at the 
end of the stroke. Others claim that it is better 
to have about five pounds above the atmosphere. 
Probably either one will give g-ood results within 
reasonable limits, but with a very light load, if we 
should attempt to lower the boiler pressure to 
meet this requirement, it would be so low that it 
would prove to be unprofitable, for althoug-h 
when we expand the steam below the pressure of 
the atmosphere the condensation is excessive, 
still it proves to be a less evil than to run with a 
low boiler pressure. If we were running- with a 
gage pressure of 75 pounds on the boilers, and 
the load is such as to g-ive a high terminal press- 
ure, say 35 pounds absolute, if we raise the boiler 
pressure to 100 pounds, the expense for fuel will 



140 MODERN EXAMINATIONS 

be much less, taking- it for granted that the 
boilers are safe at the hig-her pressure. In the 
case of a compound condensing* engine there are 
other matters to take into consideration, which 
do not apply to a simple engine. 



OF STEAM ENGINEERS. 141 



CHAPTER XXIX. 

SIMPLE AND COMPOUND ENGINES. 

If we are running- a simple, non-condensing-, 
automatic eng-ine, and for any cause wish to raise 
the terminal pressure, all that we have to do is to 
lower the boiler pressure, and the desired result 
is obtained, and that is all that there is to it; but if 
we have a compound condensing- eng-ine and the 
terminal pressure in the high pressure cylinder 
is too low to g-ive g-ood results, there are several 
things to be taken into consideration. Let us 
follow the operation and note the results. If the 
terminal pressure in the hig-h pressure cylinder is 
very low, then but little steam will be left to g-o to 
the low pressure cylinder, and an uneven distri- 
bution of the load is a natural consequence. Now 
if we can raise this terminal pressure it will make 
a difference, and so we proceed to lower the 
boiler pressure. Assuming- that the load is a 
constant one, the first thing* that we notice is that 
the point of cut-off is lengfthened, and the steam is 
not expanded down as low as it was formerly. 
We now have more steam g-oing- to the low press- 
ure cylinder, and its mean effective pressure is 
raised accordingly, but as the mean effective press- 
ure of the two cylinders taken together is a con- 
stant factor under conditions named, this increase 
is not needed, and the effect of it is to cause the 
engine to make an effort to increase its speed, but 
this effort is promptly checked by the governor, 



142 MODERN EXAMINATIONS 

which shortens the point of cut-off, the effect of 
which is to reduce the mean effective pressure in 
the hig-h pressure cylinder, and also in the low 
pressure, and as our terminal pressure in this 
cylinder is now raised, we shall need more water 
to condense the steam, as a hig-her pressure 
means more heat to dispose of, and thus more 
work is put upon the air pump. In addition to 
this, as even now the point of cut-off is longer 
than it was before the boiler pressure was re- 
duced, more steam will be needed on this end of 
the machine also. Now the question is, have we 
gained enough to offset the loss? 

A due consideration of these facts will explain 
the necessity of having an engine of this kind 
properly proportioned for the work that it will be 
required to do, and for the power that it will be 
called upon to develop. Of course it is always 
well to have even a simple engine of a suitable 
size, but as we add on cylinders the desirability 
of it increases. 

Another question that the indicator helps us to 
decide, in the case of a compound engine, is 
whether it pays to run a compound engine or not. 
Suppose that we have a simple, non-condensing 
engine, in which there is no back pressure above 
the atmosphere. The conditions are such that 
the horse power constant is 2.5 Now if we com- 
pound the engine, that is, add another C3dinder, 
say twice the diameter of the first one, we may 
have caused a back pressure of six pounds in the 
high pressure cylinder. This will of necessity 
cause the mean forward pressure to be increased 
by six pounds, and consequently this cylinder will 
be called upon to furnish 2.5x6 = 15-horse power 
more than it did before, and this is required to 
overcome the increased back pressure. 



OF STEAM ENGINEERS. 143 

If this were not put to some use, the compound- 
ing" would be a dead loss, but as the extra steam 
so used is to be utilized further, it changes the 
the conditions. As the low pressure cylinder is 
twice the diameter of the high pressure, it follows 
that the horse power constant will be four times 
as great, ignoring the areas of the piston rods, so 
that 2.5x4 = 10. 

Now, if by creating an additional back pressure 
of six pounds, calling for 15-horse power to over- 
come it, we can secure steam enough to run our 
low pressure cylinder, securing for it a mean 
effective pressure of three pounds, then it shows 
on the face of it that it pays to compound, for 
when we trade off 15 horse power and get 30 in 
return for it, we are on the safe side, to say the 
least. It is assumed that the extra water needed 
will not have to be bought of the local corporation 
monopoly, provided we wish to add a condenser 
to this engine. 

The indicator does not tell us everything that 
we wish to know in this connection, however, for 
it does not point out the difference in cylinder 
condensation, which is often referred to as X on 
account of its being an unknown quantity, but as 
the terminal pressure in the high pressure cylin- 
der is higher, it is only reasonable to suppose 
that the condensation will be less in proportion as 
the difference between the initial and the ter- 
minal pressure is less. 

If we now add a condenser, and thereby remove 
a large part of the back pressure on the large 
piston, we shall make another improvement, for 
the air pump deals with this atmospheric press- 
ure in a more economical way than the piston can, 
therefore it is good policy to make the second 
cylinder much larger than the first, the ordinary 



144 MODERN EXAMINATIONS 

limit being" twice the diameter, or four times the 
area, but a more common practice is to make 
them as 16 is to 30 inches, or as 22 is to 40 inches, 
respectively, in diameter. For cross compounds it 
is customary to make the piston rods of the same 
diameter, notwithstanding- the great difference in 
the size of the pistons, on account of the differ- 
ence in the mean effective pressures acting on 
them. 



OF STEAM ENGINEERS. 145 



CHAPTER XXX. 

CALCULATING THE AMOUNT OF WATER NECESSARY 
TO SUPPLY A SURFACE CONDENSER. 

Some time ago a friend in another state re- 
quested the writer to inform him how much water 
he would need, provided he added a condenser to 
his eng-ine. He stated that it was a compound 
engine, gave the diameters of the cylinders, length 
of the stroke and pressure carried on the boiler. 
As the point of cut-off was not given, nor any 
data from which the terminal pressure could 
be calculated, it was not possible to give an in- 
telligent answer. This then is another matter 
that the indicator helps us to decide, namely, the 
volume of circulating water that will be required 
for any engine under stated conditions. 

This problem we intend to illustrate and ex- 
plain in full, beginning with a formula given us 
for this purpose: 



1114+.3T-/ 

=V. 

t'-t" 
In which T=temperature of steam entering con- 
denser, /=temperature of feed water, ^'^ —temper- 
ature of water of condensation discharged, and 
/"=temperature of circulating water, all in de- 
grees P., and V=volume of water. 

This formula may be read as follows: To the 
constant number 1114 add .3 of the temperature 



146 MODERN EXAMINATIONS 

of the steam as it enters the condenser (expressed 
in deg-rees Fahrenheit). Prom the sum so ob- 
tained, subtract the temperature of the feed 
water. Divide the remainder by the temperature 
of the water of condensation as discharg-ed, minus 
the temperature of the circulating- water before it 
is taken up by the circulating- pump. The quo- 
tient will be the volume required ; or, in other 
words, it will be the number by which you must 
multiply the number of pounds that is required 
per hour to g-enerate the steam that is used in 
operating- the eng-ine. The product will be the 
nnmber of pounds needed per hour to supply the 
condenser. 

In calculating- the amount of water that will be 
needed it is well to remember that while it is a 
g-ood idea to continue to pump the feed water 
throug-h a heater, still it must not be expected 
that it will be as hot as formerly, as the pressure 
in the exhaust pipe wnll be g-reatly reduced by the 
condenser and air pump. Also that after the con- 
denser has been added the back pressure will be 
reduced, thus requiring- less forward pressure, 
the consequence being- that the terminal pressure 
will be less (as before stated), making- the tem- 
perature of the exhaust steam as it g'oes to the 
condenser lower than when it is exhausted into 
the atmosphere. Therefore w^e may safely as- 
sume a lower temperature for it, or if we choose 
to take it as we find it, whatever error there is 
will be on the safe side, as the result so obtained 
will be more than what is actually needed, but the 
difference will not be g-reat. 

We now call attention to Fig. 8, Avhich consists 
of diagrams from the hig-h pressure cylinder of a 
compound condensing- eng-ine, the data being- as 
follows: Diameter of cylinder 12 3-16 inches, 



OF STEAM ENGINEERS. 



147 



stroke 36 inches. Diameter of piston rod 2}i 
inches. Net area of piston, obtained by subtract- 
ing" one-half area of rod from area of piston 
114.9033 square inches. Horse power constant 

Fi<5.8. 




1.5041. Mean effective pressure of right hand 
card, 20 pounds, left hand card 23 pounds, and of 
both tog-ether 21.5 pounds. Indicated horse power 
32.338, terminal pressure (absolute), rig-ht hand 
card 25, left hand card 28 pounds, the averag-e 
being- 26.5 pounds. Pig-. 9 consists of cards from 
the low pressure cylinder of the same eng-ine, the 
data being- as follows: Diameter of cylinder 20 
inches, stroke 36 inches, diameter of rod 3 inches, 
net area of piston 310.6257 square inches, horse 
power constant 4.0663, mean effective pressure, 
rig-ht hand 10.5 pounds, left hand 10 pounds, and 
of both tog-ether 10.25 pounds. Indicated horse 
power 41.679, terminal pressure of rig-ht hand 7.5 
pounds, of left hand eight pounds, the average 
being 7.75 pounds. 



148 



MODERN EXAMINATIONS 



In determining" the horse power developed by 
this or any other compound or compotmd con- 
densing eng-ine, all that is necessary is to add to- 
gether the horse power developed in the two 
cvlinders. In this case it is 32.3384-41.679= 74.017 




horse power. The initial pressure is but 80 
pounds. As the lowest terminal pressure is 7.5 
pounds, we will assume that the feed-water is 
heated to 130°, that the steam as it enters the con- 
denser has a temperature of 180°, the temperature 



OF STEAM ENGINEERS. 149 

of the water of condensation discharged is 100°, 
and that of the circulating* water 70°. Our prob- 
lem, therefore, is as follows: 



1114+.3X 180-130 

=34.6 volumes. 

100-70 

We w^ould call attention to the fact that if the 
temperature of the discharged water is 110°, the 
value of V will be 25.95, instead of 34.6 as above, 
which will make a great difference in the work of 
the circulating pump, and will be quite an object 
when the supply of water is limited. The next 
step is to ascertain the amount of water that this 
engine calls for per hour, which we will do by one 
of the rules already explained, and that may be 
found in Chapter 23. 

The high pressure cylinder has an area of 
116.6766 square inches, and its length is 36 inches. 
116.6766x36=4200.3576. Add ^ve per cent, for 
clearance and we have 4200.3576+210.0178=4410.- 
3754 cubic inches. Dividing this by 1728 gives us 
2.5523 cubic feet per stroke, and as this engine 
runs 72 revolutions per minute, we have 144 
strokes to calculate on, and 2.5523x144=367.5312 
cubic feet per minute. 

The average terminal pressure of these cards is 
26.5 pounds. The weight of one cubic foot of 
steam at 26 pounds pressure is .0650 pound, and 
at 27 pounds it is .0673 pound, therefore .0650+ 
.0673— 2= .06615 pound, which is the weight at 
26.5 pounds pressure; 367.5312 X. 06615 =24.3121 
pounds per minute, and multiplying this by 60 
gives us 1458.726 pounds per hour. One gallon of 
water weights 8.3 pounds, and 1458.726-^8.3 = 
175.75 gallons per hour, which is the water ac- 
counted for by the indicator. 



150 MODERN EXAMINATIONS 

Referring" to a preceding- part of this calcula- 
tion, we find that we need 34.6 volumes, and 
175.75x34.6=6080.95 g-allons per hour. It may 
be of interest to note the efficiency of this engine, 
and as the indicator accounts for 1458.726 pounds 
of steam per hour, and as the total horse power 
developed is 74.017, we divide the former by the 
latter, and our quotient is 19.7 pounds of steam 
per horse power per hour. 

If this were a larger engine, using steam at say 
130 povinds pressure, and with a load for which it 
is adapted, we should expect a g-reater efficiency; 
or, in other words, less steam per horse power 
per hour would be used, but when we consider the 
size of it, the low initial pressure of 80 pounds 
and the slow speed, we admit that it is doing* very 
well. 

It was formerly a simple engine, but as the load 
was increased the low pressure cylinder was added 
and it is now g-iving good satisfaction, using less 
fuel than before, and doing the work easily. 



OF STEAM ENGINEERS. 151 



CHAPTER XXXI. 

THE AMOUNT OF WATER NECESSARY FOR A JET 
CONDENSER. — DENSITY OF STEAM. 

As will be noted the formula g-iven in Chapter 
30 applies to the use of a surface condenser, and 
it will no doubt be of interest to explain the for- 
mula g'iven us for use in the case of a jet con- 
denser, as many of them are in use, and still more 
will be used in the future. 

We shall first give a formula to determine the 
amount of water that will be required to reduce 
steam of any given pressure to water of a stated 
temperature, as follows: 
S+L-D 

=V 

D-I 
In which S = sensible heat of the steam, L=latent 
heat of steam, D=temperature of discharg'ed 
water, I=temperature of injection water, and V = 
volume of water as compared with that which it 
required to generate the steam. 

When written out in full this will read as fol- 
lows: Add the sensible and latent heat of the 
steam expressed in degrees F. together, and from 
the sum so obtained subtract the temperature of 
the discharged water. Divide the remainder by 
the number obtained by subtracting the tempera- 
ture of the injection water from the temperature 
of the discharg'ed water, and the quotient will be 
the volume required. We will now apply this to 



152 MODERN EXAMINATIONS 

the case mentioned, and illustrated in Chapter 30, 
Fig's. 8 and 9, but we must take the steam as it 
leaves the low pressure cylinder for the con- 
denser, as that is what we must condense. The 
lowest terminal pressure here is 7.5 pounds, and 
as it is but 8 pounds at the other end, the differ- 
ence in temperature being- but 3°, we will take the 
lowest as before. 

If the difference was g^reater we should take the 
averag-e. Substituting for the symbols their 
values, we have 

180+988-100 

=35.6 volumes. 

100-70 
The diag"rams call for 175.75 g-allons per hour, 
which is one volume, and 35.6 volumes equal 
175.75x35.6 = 6256.7 g-allons per hour. When the 
temperature of the steam is g-iven, instead of the 
pressure, the formula is as follows : 
l+T-t 

=V. 

t—w 
In which /=latent heat, T = temperature of steam, 
/=temperature of discharg-e, zf = temperature of 
condensing- water, and V = volumes. Substituting- 
for the symbols their values as above, we have 
988+180-100 

=35.6 volumes. 

100-70 
This operation is practically the same as the one 
preceding- it, but both are g-iven in order to cover 
all the g-round. 

The next question that naturally sug-g-ests itself 
in this connection is, how shall we determine the 
area of the pipe that is to convey this injection 
water to the condenser? It may be determined 
by the following* formula: 



OF STEAM ENGINEERS. 153 

A C 

=X 



V 

In which A = volume of water required for g-ener- 
ating" the steam used, expressed in cubic inches 
per second, C = number of volumes of water re- 
quired for condensation, V=velocity due to flow 
in feet per second and X = areain square inches. 
This is a very innocent looking- formula, but it 
will require some patience on the part of any one 
not familiar with it, in order to fully understand 
the meaning of every part of it. However, it is 
not ver}^ complicated, although the explanation 
ma}^ seem somewhat lengthy. 

The first step is to read the formula, in order 
to avoid the possibility of a misunderstanding 
here, which we will do as follow^s: Multiply A by 
C and divide the product by V, and the quotient 
will be the area of the pipe in square inches. We 
will now determine the value of A by use of the 
following rule: To compute volume of water in a 
given volume of steam, multiply the volume of 
steam in cubic feet by its density, and the product 
will be the volume of water in cubic feet. By re- 
ferring to Chapter 30 we see that the engine from 
which the diagrams illustrated there were taken 
calls for 367.5312 cubic feet of steam per minute, 
but as the time mentioned in this problem is sec- 
onds, we will divide by the number of seconds in 
a minute, and 367.5312-^-60 = 6.12552 cubic feet per 
second. 

Here a few words concerning the density of 
steam will not be out of place, for in the tables of 
properties of saturated steam that are published 
in the various books of reference, there is one 
column under the heading of "Densit}^ or weight 
of one cubic foot." This may mislead the casual 



154 MODERN EXAMINATIONS 

reader into thinking- that density and weight are 
synonomous terms, but such is not the case, for 
the weight refers to the actual weig-ht of a cubic 
foot of steam, while density means the weig-ht of 
it as compared with the weight of a cubic foot of 
water, and taking- this as 62.5 pounds, it is a prob- 
lem in proportion as follows: As 62.5 is to 1, so 
is the weight of the steam as to its density. In 
the case in hand, the pressure is 26.5 pounds ab- 
solute, as before shown, and we have already 
demonstrated that a cubic foot at this pressure 
weig-hs .06615 pound, therefore 62.5 : 1 : : .06615 
: .0010584, which is the density at stated pressure. 
As will be noted, the process consists of simply 
dividing- the weig-ht of the steam per cubic foot by 
62.5, although this does not explain the reason 
for the proceeding-, as when viewing it as an ex- 
ample in proportion, and it therefore follows that 
when the density is g-iven and the weig-ht desired, 
the process is reversed, or in other words, sub- 
stitute multiplication for division, so that the 
density multiplied by 62.5 will g-ive the weight. 



OF STEAM ENGINEERS. 155 



CHAPTER XXXII. 

DETERMINING THE AREA OF INJECTION PIPE. 

Proceeding- with our problem we have 6.12552 X 
.0010584 = .006483 cubic feet of water per second. 
As we wish to have it in cubic inches, we multiply 
by the number of cubic inches in a cubic foot, and 
.006483x1728 = 11.2 cubic inches per second. 
Adding- 10 per cent, for leakage of valves, etc., 
makes it 12.32, which is, therefore, the value of A. 
The value of C is 35.6 as demonstrated in Chapter 
31. 

In determining- the value of V, it is necessary 
to know the vacuum in the condenser, and in this 
case it is stated at 25 inches. To reduce to 
pounds, divide by 2.04, and 25h-2.04 = 12.25 
pounds. To ascertain flow of water in feet per 
second due to this vacuum, multiply by 2«31 in the 
case of fresh water, 12.25x2.31 = 28.29 feet. To 
this must be added the vertical distance or heig-ht 
from centre of opening* in condenser to surface of 
water above the condenser, assuming that it is 
above it. 

This is not stated on the diagrams taken from 
this engine, but we will assume it to be eight feet. 
Then 28.29+8 = 36.29 feet per second. Thus we 
have established the value of V in the formula, 
and when we substitute for the symbols their 
values, it stands as follows: 
12.32x35.6 

=12.1 

36.29 



156 MODERN EXAMINATIONS 

square inches, or practically a pipe four inches in 
diameter will be needed for this case, provided 
the water supply is near at hand, but if a long 
pipe is necessary, a larger size should be used. 
The author would call attention to the fact that 
this formula is a modification of one found in 
a certain standard book of reference, but it will 
answer for all ordinar}^ conditions, and for small 
and medium-sized engines. It may be well to 
write it 

A C 

= X 

V D 
in which case D would be a variable factor, to be 
changed to suit certain conditions, at the judg- 
ment of the engineer. 

There is another wa}^ to determine the value of 
A, as follows: The amount accounted for by the 
indicator is 175.75 gallons per hour. Dividing 
this by 60 gives us 2.929 gallons per minute, and 
dividing this quotient by 60 gives us .0488 gallons 
per second. As there are 231 cubic inches in a 
gallon, .0488x231 = 11.2 cubic inches per second, 
and adding 10 per cent, makes it 12.32 as before. 
Here it will be noted that the value of V is 
calculated on a fresh water basis, but if salt water 
is to be used, as we may with a surface con- 
denser, then we must multiply the vacuum in 
pounds by 2-24, instead of 2.31, for, as salt water 
is heavier, it does not require so high a column to 
correspond to a stated amount of vacuum. 

And again we have assumed that the water of 
condensation is above the condenser, but it often 
is below it, which changes the conditions, for in 
the former case the distance in feet must be added 
to the height due to the vacuum, as it helps the 
water in its passage, but in the latter case, with 



OF STEAM ENGINEERS. 157 

the supply below the condenser, it must be sub- 
tracted from it, as it tends to retard the flow of 
the water. Suppose then that we assume that we 
are to use sea water, which is eight feet below the 
centre of the opening* in condenser. In that case 
the value of V would be 12.25 X 2.24-8=^19.44, 
making- the problem stand thus: 
12.32x35.6 

=22.56 

19.44 
square inches, or in other words, requiring- a 
pipe about ^ve inches in diameter. 

This conclusion is only a reasonable one, for 
every eng-ineer knows that when a pump has the 
water delivered to it under pressure, the pipe may 
be much smaller than when it must be raised in the 
ordinary way. From the foreg-oing' calculations 
it will be seen that it is very necessary to take 
g-reat care in taking- a diag-ram from an eng-ine, to 
see that the indicator is in good order and that it 
is well lubricated. The paper should be smooth 
and toug-h, althoug-h not necessarily g-lazed. The 
pencil should be sharp that it may make a fine 
line, and so adjusted that it will not bear too 
hard, for in that case the card or diag-ram will be 
distorted, and prove worse than useless. 

It is for the best interests of every man now in 
charg-e of a steam plant or who expects to be in 
the future, to understand the use of this instru- 
ment, for although the engineer in charge of a 
small plant may not see the need of such knowl- 
edge, as he may be laboring- under the impression 
that it is only necessar\^ for those who are run- 
ning large engines, yet if the opportunity should 
present itself for him to be advanced to a more 
responsible position, provided he understood the 
indicator, it would not be a proper time for him 



158 MODERN EXAMINATIONS 

to begin to learn then, for while he would be 
getting- posted on the subject, another man would 
secure the position. Qualify for the position 
first, and seek the same afterward. Always keep 
the horse before the cart, and never attempt to 
reverse the order. 



'i 



OF STEAM ENGINEERS. 159 



CHAPTER XXXIII. 

THREE SYSTEMS OF STEAM HEATING FOR BUILD- 
INGS. 

It is well for the applicant for a license to un- 
derstand something" of steam heating- systems, 
and their application to use in every day practice, 
as this will be necessary in many cases, for this 
apparatus will be under care of the eng-ineer, and, 
althoug-h he may be able to run a certain system 
from day to da3% provided nothing" unusual hap- 
pens, still, it is much better for him to under- 
stand the principle on which it works, for then he 
can more readily detect the cause of failure of 
any part of it to work. The writer well remem- 
bers presenting- the question: "What is the mean- 
ing- of the term indirect radiation?" before an 
assembly of eng-ineers, and not one of them could 
g-ive a satisfactory reply, therefore it may be well 
to g-ive a description of the three principal sys- 
tems of heating- building-s, namely, direct radia- 
tion, indirect radiation and direct-indirect radia- 
tion. 

The first is just what its name applies, and that 
is that the heat is radiated directly into the room 
to be warmed from coils or radiators located in 
said room. The pressure may be hig-h or low, 
and steam or hot water may be used, but so long- 
as the radiators are in the room to be heated, and 
are not connected with any system of ventilation, 
this system is known as direct radiation. 



160 MODERN EXAMINATIONS 

The indirect radiation system is one in which 
the air is warmed by coils or banks of pipes 
located in some place outside of the room to be 
heated, and then forced by means of a fan into 
rooms where it is needed, or small separate radi- 
ators may be placed near the bottom of the flues 
leading- into the rooms, when, as the air becomes 
heated, it naturally rises, and thus can be utilized. 

It is quite evident that the fan is to be pre- 
ferred, as it makes the circulation positive, and 
does not depend on circumstances, such as "which 
way the wind blows," etc. From the nature of 
the system it will be noted that it can only be used 
in connection with some system of ventilation. 

The direct-indirect system, as its name indi- 
cates, is something* of a combination of the other 
two systems, for it is one in which the radiators 
are partly or wholly within the room to be heated, 
and are in direct connection with some system of 
ventilation. 

The indirect system is used at the present time 
for heating- factories more than ever before, and 
the apparatus is very simply, consisting- of a large 
coil or bank of pipe through which the exhaust 
steam from the engine circulates, or when it is 
not running-, live steam from the boiler is intro- 
duced. The coil is encased in a jacket of sheet 
iron, or of something- more substantial if it is very 
large, and a fan blower forces the cold air into 
this jacket, where it is heated, and is then led 
away by means of suitable pipes to the different 
rooms where it is needed. The fan is often run 
by a small independent engine, and so equipped 
that the speed may be varied at will. One great 
advantage of this system is that while it heats it 
also ventilates, and in summer time cool air may 
be forced throug-h, and the rooms rendered more 



OF STEAM ENGINEERS. 161 

comfortable. Care should be taken to have the 
inlet for air in such a place as to secure that 
which is pure and wholesome, as the odor of the 
rooms will be unpleasant otherwise. 

The direct-indirect system reminds one of a 
factory, the main part of which has been out- 
grown by the business carried on therein, and to 
provide necessary room, additions are built on 
from time to time, until the whole affair has a 
patched-up appearance. So it is with this system, 
for while there is no doubt about its giving- good 
results in many cases, still it is not as symmetri- 
cal as the others, and involves unnecessary com- 
plications. 

The direct radiation system for steam is prob- 
ably used more than any other for heating- public 
buildings, and as there is more than one wa}^ to 
pipe up this system, we would call attention to 
this fact and to some of the methods adopted. 
We frequently hear the question asked: "Can the 
water of condensation from coils and radiators be 
returned to the boiler without the use of some 
mechanical contrivance made for this purpose?" 
To this we would reply that it can and is done in 
many places, and we see no objection to it. 

Of course the radiators must be above the water 
line of the boiler, and it is a good plan to have the 
piping so arranged that the cold water which fills 
the returns when steam is first turned on may be 
blown out into the sewer (through suitable con- 
nections), and when the body of water is in mo- 
tion and circulation established, the blow-off valve 
may be closed, when the water will be returned to 
the boiler. The author is aware that this has 
been tried, and in some cases proved a failure, but 
wherever it has there is some straight reason for 
it. It is necessary to maintain boiler pressure in 



162 



MODERN EXAMINATIONS 



the radiators, and if there are so many of them 
that the opening in the dome or the intermediate 
pipes are not large enough to supply sufficient 
steam to do this, then the water of condensation 
cannot return to the boiler, unless it is pumped 
in. This is the principal cause of failure. 

If some of the radiators must be located lower 
than the water line, it will be necessary to provide 
a pump or trap to return the water of condensa- 
tion. 



OF STEAM ENGINEERS. 163 



CHAPTER XXXIV. 

COMPARISONS OF SYSTEMS FOR STEAM HEATING. 

The system of direct radiation for steam heat- 
ing- may be piped up in four different ways as 
follows : (1) A main steam pipe is continued 
from the dome of boiler up to the highest floor of 
the building- to be heated. From this pipe, which 
is commonly called a riser, steam is taken for ra- 
diators located on each floor, and separate return 
pipes are provided for each, which are not con- 
nected tog-ether until fhey are broug-ht down 
below the hydrostatic level. (2) A riser is put up 
and connected in the same way as before, but the 
drip pipes are all connected into one pipe, called 
the return riser, in the same way that steam is 
taken from the steam riser, and thus returned to 
the boiler. (3) The steam riser is provided as 
before, which is also made to do duty as a return 
riser until it reaches the point where it is con- 
nected into the horizontal steam pipe from boiler. 
Here a tee is used instead of an elbow, and the re- 
turn pipe is continued down until it is below the 
hydrostatic level, when it is carried in a horizon- 
tal direction to the boiler. (4) A sing-le pipe is 
the only connection between boiler and radiator, 
in which the steam passes along- the upper part of 
it, and the water of condensation returns along- 
the lower part of it. As a matter of course all of 
the pipes in this circulation must incline towards 
the boiler, or else it will not work at all. 



164 MODERN EXAMINATIONS 

System No. 1 is to be recommended above the 
others, for it gives practically a positive circula- 
tion, and especially where low steam pressure is 
to be used, and in places where it will be run b}^ 
persons who are not experts, as there should be 
no trouble in expelling the air, and preventing* all 
of the disagreeable cracking noises frequently 
heard in other systems, caused by steam coming 
in contact with water, etc. Its first cost is a 
little more than either of the others. 

No. 2 is used much in large buildings, and gives 
fair results when properly put up and cared for. 
It requires less labor and material, consequently 
the expense is less. 

In No. 3 much larger pipes must be used, and 
for that reason the cost in some cases will equal 
that of No. 2, and the results will be less satisfac- 
tory. The same objections apply to No. 4, and 
therefore it is not to be recommended except for 
small jobs, or w^here for some special reason it 
may be desirable. 

Where Nos. 1 or 2 are used care must be taken 
to provide a drip connection, so that no water can 
collect in the vertical steam supply pipe or steam 
riser, for it must be remembered that the flow of 
steam through this pipe is often very slow, and 
consequently the condensation is excessive. 

It is not intended to give a complete description 
of the details of piping for these systems, as it 
would require a volume of reading matter and 
many illustrations, but the few hints and sugges- 
tions here offered will be found of practical use, 
as for instance it is better to use angle valves 
wherever practicable, as they give full opening, 
cause less friction and save the use of an elbow. 

Where a valve must be located in a straight 
pipe, a straight-way valve is preferable, but if for 



OF STEAM ENGINEERS. 165 

any reason a g'lobe valve must be used, then do 
not place the stem in a vertical position, for if it 
is, the water running- along* the bottom of the pipe 
will be trapped there, owing- to the construction 
of the valve, and much unnecessary strain will be 
brought to bear on the pipe by the hammering- 
action of this water. 

Pieces of pipe that have been broken by this ac- 
tion, under an ordinary working- steam pressure, 
have afterward been tested, and withstood 1000 
pounds pressure applied in a careful and steady 
manner. 

When steam is first admitted to a system of 
piping-, the valve should be opened very slowly, as 
the first steam that enters will be condensed, 
causing- what is called "water hammer," therefore 
it should be admitted as carefully as possible. If 
a g-lobe or angle valve is used, it is much easier to 
tell just when it beg-ins to open than it is in the 
case of a g-ate valve, and, as it frequently happens 
that we only wish to admit a little steam to a radi- 
ator in moderate weather, this is one thing- in 
their favor. This refers to radiators having- inde- 
pendent drips. 

The eng-ineer who is systematic and careful 
about his work, and takes pride in seeing- it prop- 
erly done, always likes to have a valve stem placed 
in either a vertical or horizontal position, and 
with a g-lobe valve, the latter is the best of the 
two, but neither one of them are just rig-ht so far 
as service is concerned, for if the former plan is 
adopted, the water will be trapped in the pipe, 
owing- to the construction of the valve, and if the 
latter is, the water will stand in the bonnet and 
leak out around the stem, therefore if the stem is 
inclined upward slig-htly it will g-ive the best re- 
sults, but at the same time does not look as well. 



166 MODERN EXAMINATIONS 

Valves should be put on with the bottom towards 
the source of pressure, so that when they are shut 
there will be no steam on the stuffing- box, for 
otherwise the valve cannot be packed without re- 
lieving* the whole system of pressure. Asbestos 
wicking- for packing" valve stems is far preferable 
to the ordinary candle wicking often used for that 
purpose. 



a 



OF STEAM ENGINEERS. 167 



CHAPTER XXXV. 

DETERMINING THE RADIATING SURFACE NECES- 
SARY TO HEAT A ROOM OR BUILDING. 

If the candidate for a license is called upon to 
g"ive a rule for determining the heating or radiat- 
ing- surface necessary to warm a certain room, he 
should reply that there can be no inflexible rule 
given for such a purpose, as it will depend largely 
upon the conditions existing in each individual 
case, such as the location of the room, the manner 
in which the walls are built, the number and size 
of windows that it contains, and the temperature 
that must be maintained in it. There are, how- 
ever, rules that may be used for the foundation of 
such a calculation. The following is said to be in 
use among some of the steam fitters who put in 
heating apparatus, and many consider that it g'ives 
good results. 

Multiply the length, breadth and height of the 
room, in feet, together, and from the product so 
obtained cut oif two figures from the right hand, 
and call the remainder square feet of heating sur- 
face, or, as some might call it, radiating surface. 
This is for a high pressure S3^stem, but for a low 
pressure one additions must be made according to 
the judgment of the engineer in charge, for an 
exposed room will need more heat than one that 
is well protected, and if there are many windows 
in it, that will also be a consideration, for glass is 
a good conductor of heat. For an illustration I 



168 MODERN EXAMINATIONS 

shall take a room in the immediate vicinity of 
where this is written. 

It is 30.5 feet long, 17 feet wide and 11 feet high ; 
30.5x17x11=5703 cubic feet. As about two- 
thirds of this room is exposed, we will add 50 per 
cent, on this account, and we have 5703+2851= 
8554. Cutting- oif the two right hand figures 
leaves 85 square feet of heating surface, or about 
247 feet of one inch pipe. This rule, however, is 
not a very satisfactory one, as it does not take 
into account all existing conditions. It may be 
called a "rule of thumb." 

Now while a glazed window admits the heat of 
the sun, if it is shining directly on it, more than a 
brick wall or other opaque surface will, still, if 
the sun is not shining on it, then the glass be- 
comes an important factor in the calculation, as it 
will cool off the room much faster than brick 
walls, sheathing or lath and plaster will. The 
following rule has the endorsement of an eminent 
authority on steam heating: Divide the difference 
in temperature between that at which the room is 
to be kept and the coldest outside atmosphere, by 
the difference between the temperature of the 
steam pipes and that at which you wish to keep 
the room, and the quotient will be the square feet, 
or fraction thereof, of plate or pipe surface to 
each square foot of glass or its equivalent in wall 
surface. 

We will now explain the way to reduce wall sur- 
face to its equivalent in glass surface, and for this 
purpose we will introduce the following table 
from "Steam Heating for Buildings," by William 
J. Baldwin. Table of approximate power for 
transmitting heat, of various building substance 
compared with each other: 



OF STEAM ENGINEERS. 169 

Window glass looo 

Oak and walnut sheathing on walls 66 to loo 

White pine and pitch pine 80 to 100 

Lath and plaster walls, good 75 to loo 

Lath and plaster walls, common , 100 to 105 

Common brick (rough) 150 

Common brick (hard finish) 200 

Common brick (hard finish, hollow walls). . 150 

Sheet iron iioo to 1200 

"In fio-uring- wall surface, etc., multiply the 
superficial area of the wall in square feet by the 
number opposite the substance in the table and 
divide by 1000 (the value of glass). The product 
is the equivalent of so many square feet of g-lass 
in cooling power, and may be added to the win- 
dow surface and treated in the same way." 

Let us now apply this rule to the case of the 
room mentioned before and note the result. It is 
17x30.5 feet, so that there are 518.5 square feet in 
the ceiling-, and the same amount in the floor, 
making' 1037 square feet in both. This surface is 
taken into account because the room is in an iso- 
lated building- comparatively, there being- no other 
rooms above or below it to assist in keeping- it 
warm. 

In the sides of this room there are 30.5x11x2 
= 671 feet. In the ends 17 X 11 X 2= 374 feet, mak- 
ing- 2082 square feet in all. A part of this is glass 
surface and the remainder is hard pine sheathing, 
and as the two represent different values, we must 
separate them and reduce them to a common 
standard. There are seven windows, each con- 
taining- 11 square feet of glass, and one sash door 
with nine feet. 11x7+9 = 86 square feet; 2082- 
86 = 1996. Thus we have 86 square feet of g-lass, 
and 1996 square feet of hard pine sheathing- to pro- 
vide for. 



170 



MODERN EXAMINATIONS 



The latter we will reduce to its equivalent in 
g-lass surface, and add the two together. As this 
table tells us that the pitch pine sheathing- is 
valued at from 80 to 100 we will take it at 90 for 
an average. 1996x90^1000 = 179, which is the 
surface of the sheathing in the room reduced to 
its equivalent in glass surface. To this must be 
added 86 feet of glass surface, and 179+86 = 265 
square feet. 



OF STEAM ENGINEERS. 171 



CHAPTER XXXVI. 

AREA OF MAIN STEAM PIPE FOR DIRECT RADIAT- 
ING SYSTEM OF STEAM HEATING. — SIZE 
OF BOILER REQUIRED. 

We will now proceed to assume conditions in 
order to enable us to finish working* out the ex- 
ample presented in Chapter 35. Assuming* that 
the coldest outside temperature is at zero, or at 
0°, and we wish to warm the room so that the 
thermometer will stand at 70°, we have 70°— 0= 
70°. And here the question presents itself as to 
what we shall do if the coldest outside tempera- 
ture were taken at 10° below zero. In that case 
we would subtract the difference, as before, and 
add 10 to the remainder. A practical way to de- 
cide it is to take a thermometer in hand and calcu- 
late or count the difference in deg^rees. If we 
carry 60 pounds pressure on our heating pipes, 
the temperature will be 307°. 

The temperature of the room being- 70, we have 
307-70=237, and 70 --237 =.295. Add 50 per cent, 
for ventilation, air leaks, etc., and .295-[-.147 = 
.442, which is the number of square feet of heating 
suface needed for each square foot of glass sur- 
face, or its equivalent. In this case it is 265, and 
265 X. 442= 117 square feet, or about 340 feet of 
one-inch pipe. Now let us assume different con- 
ditions and compare results. Suppose that the 
difference between the inside and outside temper- 
atures is 70°, and we are using steam at two 



172 MODERN EXAMINATIONS 

pounds pressure. Then we would have 219—70= 
149, and 70 -=-149 ==.47. Add 50 per cent, as be- 
fore, and it brings it up to .705 square feet of 
radiating' surface for each square foot of g"lass 
surface, or its equivalent, 265 X. 705= 186 square 
feet, or about 540 feet of one-inch pipe. 

Now suppose that we wish to estimate what 
piping", boiler capacity, etc., will be needed to heat 
a building- containing- 12 rooms like the one before 
mentioned, the system to be direct radiation, and 
low pressure, say two pounds. In such a case we 
would not fig-ure in the floors and ceiling-, as they 
would not be exposed as in the case of an isolated 
room; 2082 — 1037=1045 square feet in the sides 
and ends of one room. In 12 rooms there would 
be 1045x12=12,540 square feet. In each room 
there would be 86 square feet of g-lass, and 86x12 
=1032 square feet; 12,540-1032x11,508 square 
feet of pine sheathing- to be reduced to its equiva- 
lent in square feet of g-lass, and 11,508x90-^1000 
=1035; 1032+1035=2067 square feet of g-lass, or 
its equivalent. 

Assuming- a difference of outside and inside 
temperatures amounting- to 70° as before, and a 
difference between the pipe and the room of 149°, 
and our multiplier is found to be .47, or if we 
wish to add the 50 per cent, here it makes it .705. 
Now 2067 X. 705 =1457 square feet oi radiating' sur- 
face needed, which would be about 4229 feet of 
one-inch pipe. 

Our next move is to determine the area of the 
main steam pipe, w^hich, of course, must be based 
on the number of square feet of radiating* surface 
that it must supply steam for, and to the number 
already obtained must be added the surface con- 
tained in the main itself. 

This we can only assume, but if we call it 20 per 



OF STEAM ENGINEERS. 173 

cent, of the other, it will answer our purpose. 
This amounts to 291 square feet, and 1457+291 = 
1748 square feet. Competent authorities tell us, 
and practice shows them to be correct, that for 
each 100 square feet of heating- surface in the 
building-, the main steam pipe should contain the 
area of a one-inch pipe, or .7854 of a square inch. 
1748--100 = 17.48x.7854 = 13.7 square inches. Now 
the actual internal area of what we ordinarily call 
a four-inch pipe is stated at 12.7 square inches. 
Therefore a four-inch pipe will answer our 
purpose. 

Another w^ay to tell what the diameter of the 
main steam pipe should be, is as follows : Having- 
found the number of square feet of heating- sur- 
face needed, extract the square root of it, and 
one-tenth of this number will be the desired diam- 
eter. The square root of 1748 is 41.8+ and one- 
tenth of this is 4.18, or a four-inch pipe as before. 
Probably many building-s of this size are supplied 
with steam by a smaller pipe than this, but it does 
not necessarily follow that the best results are 
obtained thereby. 

In regard to the amount of heating- surface in 
the boiler that will be needed to supply steam for 
these rooms, if there is one square foot of sur- 
face exposed to the direct action of the tire, for 
each six square feet of radiating- surface, it will be 
sufficient for the conditions before mentioned, 
provided the firing- is attended to in a proper 
manner. This would call for a boiler containing 
about 300 square feet of direct heating surface. 
If a portion of it is tube or flue surface, a large 
allowance must be made, as its efficiency is much 
less. If a horizontal multitubular boiler is to be 
used, it should be four feet in diameter and 12 
feet long, having, say 36 three-inch tubes. This 



174 MODERN EXAMINATIONS 

g-ives 150 feet of direct heating* surface, and about 
300 feet of tube surface. 

It should be noted that the data given here is 
for a system of direct radiation for steam. 



I 



OF STEAM ENGINEERS. 175 



CHAPTER XXXVII. 

HEATING WITH EXHAUST STEAM. 

Occasionally we meet an eng-ineer who does not 
appreciate the value of exhaust steam for heating" 
purposes, as they allow it to g^o to waste, or at 
least they only utilize a portion of it in heating" 
the feed water, and althoug"h it does not pay to 
cause excessive back pressure on the eng-ine, still 
if the system of piping is properly arrang-ed, all 
of the exhaust steam left after passing" throug"h 
the heater, may be used during" the winter season 
with very little detriment on account of back 
pressure. The cost of such steam in any case 
may be calculated in the following" way : 

Ascertain the horse power constant of the en- 
g-ine, and multiply it by the back pressure due to 
the weig-hting" of the back pressure valve. The 
result will be the horse power expended in forc- 
ing* the exhaust steam around the factory. Sup- 
pose that we have an eng;ine 24x60 inches running" 
at 60 revolutions per minute. When the back 
pressure valve is up or open, the back pressure is 
one pound above the atmosphere, and when it is 
down or closed, it is two pounds above it, what 
do^s it cost to use the exhaust steam for heating"? 
The horse power constant for this eng-ine is 
8.225, so that when we multiply it by the one 
pound additional back pressure caused by closing" 
the back pressure valve, and forcing" the steam 
throug-h the heating- pipes, we see that we can util- 
ize a larg-e volume of steam at a very slight cost. 



176 MODERN EXAMINATIONS 

If the piping is properly arranged this can be 
accomplished, but at the same time we do not 
recommend that any engineer figure it up in his 
own case on this basis, unless he knows just what 
the back pressure is, for it is quite possible to 
have matters so arranged that it will cause 10 
pounds back pressure instead of one. 

In many cases the exhaust pipe is carried up to 
the top of the factory, even when it is a high one, 
in order to get the exhaust steam away from the 
windows, and if it is provided with ample drips, 
or rather drip pipes, located at its lowest point, 
the steam may be carried up and cause very little 
back pressure, as it does not take much to force 
steam up, but, on the other hand, it requires 
much more to raise water. Cases can be found 
where the drip pipe is located at some point con- 
venient of access, without regard to whether it is 
at the lowest point or not. 

While such an arrangement may not cause any 
part of the exhaust pipe to entirely fill with water, 
still if there are two or three inches of water 
standing in an eight-inch pipe it will cause the 
steam at the end of the exhaust pipe to appear 
very wet, giving rise to the idea that the boiler 
primes badly, when such is not the case, and caus- 
ing unnecessary back pressure on the engine. 

With the exhaust pipe carried up at one end of 
the building, and tees having been put in at suita- 
ble places, say eight feet above each floor, if the 
ceiling is high enough to admit of it, then nipples 
may be put m, and other tees connected, from 
which branch pipes may be carried to either side 
of the room, where they are connected into a coil 
on eacli side. This is preferable to one large coil 
over the centre, not only on account of a better 
distribution of the heat, but because by placing 



OF STEAM ENGINEERS. 177 

valves at the inlet and outlet of each coil, one of 
them may be shut off in moderate weather, and 
where the building* is so situated that the sun 
shines on one side of it during* the forenoon, and 
on the other side during* the afternoon, the steam 
may be put on the coldest side of room, thus 
nearly equalizing* the temperature of the same. 
These coils should all g^radually incline from the 
main exhaust pipe toward the other end of the 
rooms, allowing* them a pitch of about one-half 
inch for every 10 feet in leng-th. At the other end 
of the factory there should be a vertical pipe of 
about one-quarter of the diameter of the exhaust 
pipe, into which all the drips from the coils 
should be connected. The lower end of this pipe 
should be attached to a g-ood steam trap, for then 
no steam will be blown out near the windows. In 
this pipe, above the hig*hest drip connection, there 
should be a valve, and from the valve the pipe 
should be continued up throug-h the roof. Thus 
the air will be readily removed when the engine is 
started and the back pressure valve is closed, and 
the trap will take care of all of the water. If ib is 
desired to put on live steam when the engine is 
not running-, the valves near the exhaust pipe may 
be closed, and also the hig-hest valve in the vertical 
drip pipe, or what mig'ht be called the main return 
riser, and the live steam turned on at pleasure. 



178 MODERN EXAMINATIONS 



CHAPTER XXXVIII. 

DIAMETER AND HORSE POWER OF SHAFTING. 

A knowledg-e of the streng-th of shafting- of 
various kinds may be required in this connection, 
and it is well to remember that a shaft of wroug^ht 
iron or any other material will transmit a g^iven 
horse power under certain conditions and last for 
years, while the same shaft would soon fail under 
other conditions, althoug^h the power transmitted 
is the same in both cases, or even less in the 
latter. 

The following' formula is g'iven us for determin- 
ing- the diameter of a wroug-ht-iron shaft to 
transmit a g'iven horse power under favorable 
conditions, namely, as in the case of a main shaft 
in a mill or factory, where it is well supported, 
not subjected to excessive strain from belts being- 
tighter than they should be and kept in line. It 
is one that agrees as well with g-ood practice as 
anv that can l:e found: 

3 /50 I. H. P. 

V ^d 

n 
in which I. H. P. is the indicated horse power to 
be transmitted, n = number of revolutions, and d 
= diameter of shaft. It reads as follows: Multi- 
ply 50 by the indicated horse power, and divide 
the product bv the number of revolutions per 
minute. The cube root of the quotient is the 
diameter of the shaft in inches. 

For example let us take the case of a shaft made 



it 

I 



OF STEAM ENGINEERS. 179 

of wrought iron which we wish to have tramsmit 
138 horse power, running- at 115 turns per minute. 
Substituting' for the symbols their values in this 
case we have : 

3 /50X138 

V 

115 
3.914 inches, or as the sizes ordinarily run, we 
would call it a 3 15-16 inches shaft. If the size of 
shaft and number of revolutions are g-iven, and 
the power that it will transmit is required, the 
formula is as follows: .02 n d^=I. H. P., which 
reads, multiply .02 by the number of revolutions 
per minute, and the product by the cube of the 
diameter. 

The product so obtained will be the horse 
power that the shaft will transmit. 

Suppose that we have a 3^ inch wroug'ht-iron 
shaft whose speed is 100 revolutions per minute, 
and we wish to know how much power it will 
safely transmit: .02x100x3.5x3.5x3.5 = 85.75 
indicated horse power. It will be noted that the 
power increases directly as the speed is increased, 
for if this shaft should be run at 200 revolutions, 
it would easily transmit 171.50 horse power. If 
the shaft is made of steel instead of wroug-ht iron 
the formula is as follows, the letters denoting- the 
same as in the preceding*: 

3 /31.25 I. H. P. 

V =^^ 

n 
Assuming* the elements of the preceding* case, 
except that the shaft is made of steel, and substi- 
tuting- for the svmbols their values, we have: 
3 /31.25X138 



180 MODERN EXAMINATIONS 

3.4 — inches nearly. If the size of shaft and speed 
is g-iven. and the power that it will transmit is re- 
quired in the case of a steel shaft, the formula is 
as follows: .03^ n d^=^L H. P. With a shaft 
running- at 100 revolutions per minute, whose 
diameter is 3.5 inches we would have .032 X 100 X 
3.5x3.5x3.5 = 137.2. (The author's experience 
with steel shafts has been that they are apt to 
prove treacherous as they sometimes break under 
very light loads, on account of hidden flaws). 

If we wish to use a cast iron shaft, the formula 
for determining- the diameter of it is as follows : 

3 783.5 I. H. P. 

V — -^ 

n 

the letters denoting- the same as above. Assum- 
ing- the elements of a preceding- case, and substi- 
tuting- for the symbols their values gives us the 
following: 

3 783.5x138 



115 

4.641 inches, which is the diameter of the cast 
iron shaft. If the number of revolutions per 
minute, and the diameter is given, and the power 
that it will transmit required, the formula is as 
follows: .012 n d3=I. H. P. Assuming the ele- 
ments of a preceding case and we have .012 X 100 X 
3.5x3.5x3.5 = 51.45 indicated horse power. 

The foregoing rules and formula do not apply 
to crank shafts of steam engines, propeller shafts, 
or other conditioas where the service required is 
severe. For determining the size of crank shaft 
for compound engines, with cranks set at an angle 
of 90° we have the following formula for wrought 
iron: 



OF STEAM ENGINEERS. 181 



^A/D^p+dnS 



15 

XS = 

2468 
diameter of shaft, in which D is the diameter of 
high pressure cylinder, in inches, p is the boiler 
or steam chest pressure above a vacuum, d is the 
diameter of low pressure cylinder in inches, and 
S is the stroke in inches. This may be read as 
follows: Square the diameter of the hig-h press- 
ure cylinder, and multiply by the steam-chest 
pressure absolute. To this product add the 
square of the diameter of the low pressure cylin- 
der multiplied by 15 and divide their sum by 2468. 
Multiply the quotient by the stroke in inches, and 
extract the cube root of the product which will be 
the diameter of the shaft in inches. Por the sake 
of illustrating" this formula we will suppose that a 
cross compound engine with cylinders 20 and 40 
inches in diameter, respectively, and a stroke of 
48 inches to be operated under a pressure of 140 
pounds absolute, is to be used, and we wish to 
know what the diameter of the crank shaft should 
be. Substitute for the symbols their values and 
we have the following: 



3 7202x140+402x15 

X 48 = 11.6 inches nearlv. 

2468 
In practice a 12 inch shaft would be used. 

As we wish to make every part of this book 
plain as we proceed, we will give the solution of 
this problem in detail. The diameter of the hig'h 
pressure cylinder is 20inches, which being squared 
gives us 20x20=400. The absolute pressure is 
140 pounds, and 400X140=56,000. The diameter 
of the low pressure cylinder is 40 inches, which 



182 



MODERN EXAMINATIONS 



being squared gives us 40 X 40 := 1600, and multiply- 
ing by 15 makes it 24,000. This is to be added 
to our first product, and 56,000+24,000 = 80,000, 
and 80,000-- 2468=32.41. This is to be multiplied 
by the stroke in inches, and 32.41x48 = 1555.68, 
the cube root of which is 11.6 nearly. 



OF STEAM ENGINEERS. 183 



CHAPTER XXXIX. 

WIDTH, SPEED AND HORSE POWER OF BELTING. 

Probably there are few subjects connected with 
steam eng^ineering" concerning- which there is a 
g-reater diversity of opinion than as to a proper 
rule for determining- the horse power that a belt 
will transmit, and also for g'iving- the proper 
width of belt to transmit a g-iven amount of 
power. The writer does not expect to settle the 
question b}^ anything that may be written here, 
but at the same time does not hesitate to give a 
formula that takes into consideration all, or nearly 
all of the factors in the case. It is taken from 
Nystrom's Mechanics and is to determine the 
power that a belt will transmit, and is as follows : 
BdnZS 



15,000,000 
= H. P., in which B= breadth of belt in inches; 
d equals diameter of the smallest pulley in inches ; 
n= revolutions per minute of the smallest pulley ; 
Z=half angle of contact of belt on smallest pul- 
ley; S=safe working strength of belt in pounds 
per inch of width, for ordinary single leather belt 
is taken at 100 pounds, and H. P. = the horse 
power that can be easily transmitted. For ex- 
ample, we will take the case of a belt 48 inches 
wide, running over pulleys of which the smaller 
one is 54 inches in diameter, and revolves 200 
times per minute. Half angie of contact is 85 



184 MODERN EXAMINATIONS 

degrees, and safe load 100 pounds per inch of 
width. Our problem then becomes: 
48x54x200x85x100 

= 293.7 

15,000,000 
horse power. The reason for taking- the width of 
belt into account is because each inch or fraction 
thereof will transmit a certain amount of power. 
The diameter of smaller pulley is taken because 
that effects the friction of the belt. The speed of 
it is noted because that effects the power trans- 
mitted directly, just the same as the speed of 
shafting- effects it. The term "half ang-le of con- 
tact" may need some explanation. The rim of 
the pulley is a circle, and accordingly contains 360 
deg-rees. If both of the pulleys were the same 
size, and there was no sag- to the belt, it would lap 
around one-half of this circle, or 180 deg-rees, but 
as the other pulley is assumed to be larg-er than 
this one, and the belt sag's a trifle (which is a help 
in some cases, and a detriment in others), the 
ang-le of contact is taken at 170 deg-rees, and one- 
half of this is 85 deg-rees. The safe load is deter- 
mined by experiment, but for belts in g-ood order 
may be taken at 100. The divisor is a constant 
number. 

If we wish to determine the breadth of belt 
necessary to transmit a g-iven horse power, our 
formula becomes 

15,000,000 H. P. 



dnZS 
breadth, the letters meaning- the same as before. 
Assuming- elements of the preceding- case, we 
have 15,000,000X293.7 

-= 48 inches. 

54x200x85x100 



OF STEAM ENGINEERS. 185 

These formulae apply to leather belts in good 
order, running* on clean iron pulleys. There are 
several possible conditions which tend to modify 
them, as, for instance, if a double belt is running- 
over wooden pulle3^s, or iron pulleys covered with 
leather, the efficiency will be g*reater, and if the 
belts are hard and dry, and running- over pulleys 
that are very roug'h, or extraordinarily smooth on 
their faces, the efficienc}^ will be decreased. 

If we have a g-ood double belt instead of a sing-le 
one, the value of S will be doubled, or taken at 200 
pounds, and according-lv the horse power that it 
will transmit will be doubled and 293.7x2=587.4 
horse power. 

This assumes that the belt will not slip on the 
pulley even if the load is increased until the full 
safe working- strain on the belt is reached. 
If a belt is cemented and riveted tog-ether, or in 
other words is made *' endless," it will be much 
strong-er than if it is laced in the usual way, for 
reasons that are plain to ever}^ eng-ineer who has 
g-iven the matter any consideration. 



186 MODERN EXAMINATIONS 



CHAPTER XL. 



STEAM BOILER EXPLOSIONS. 

The applicant should be well posted as to the 
causes, or perhaps we mig-ht be allowed to sa}^ the 
cause of steam boiler explosions, and also as to 
the theories which have been advanced at one time 
or another, for the same, but which can hardly be 
called correct ones in view of other facts in the 
same connection. Take for instance the theory 
of superheated water as an active ag-ent in this 
matter. 

The advocates of this theory claim that g-lobules 
of water absorb the heat of the fire in the furnace, 
and that while in a state of rest they are harmless, 
but when they rise to the surface and burst from 
some unknown cause thev develop a vast amount 
of energ-y, so much in fact, that no boiler can 
withstand the accumulation of it. 

This is said to be the condition of thing's when 
w^e shut down our engines, for while they are at 
rest it is assumed that the heat is being* g-enerated 
in the furnace, very much the same as when the 
machinery is in motion, and as the eng'ine is not 
taking- it, it is silently stored up for future use or 
abuse. So far as our observation and practice 
have been teachers, they have taug-ht us that when 
a fire is properly banked previous to shutting' 
down the eng'ine there is very little heat g-enerated 
to g-o anywhere. We are well aware that in places 
where it is necessary to force fires almost up to 



OF STEAM ENGINEERS. 187 

shutting--down time the brickwork, arch plate, 
dead plate and other parts not in contact with 
water are at a high temperature, and some steam 
will be generated by this heat after the fires are 
banked, but even then the only effect that we will 
have noticed is that the lever safety valve slowly 
lifts as the pressure accumulates, and the surplus 
passes out into the atmosphere, and we cannot 
see how it can do any more harm to the boiler 
than if the steam was used by the eng'ine. But we 
are told that when the throttle valve is opened 
to start the engine the pressure on the top of the 
water is relieved, and it therefore rises and is 
converted into steam of great force, so that no 
gage can indicate it. 

We wonder how it is that anyone can still advo- 
cate this theory after they have stood by the side 
of one of our first class passenger locomotives, as 
they stand at a station ready to start out on a 
swift journe3^ with its train of half a dozen 
coaches, for while it waits the heat is being rapid- 
ly absorbed by the water, and the pressure rises 
until the safe working pressure is reached, when 
the pop safety valve opens with such celerity as to 
cause the unsuspecting' casual observer to give an 
involuntary jump, but no explosion takes place, 
and in addition to all this, certain kinds of engines 
are started up several times each day, and sudden- 
ly, too, but no explosion follows. Cases can be 
cited, it is true, where explosions have taken place 
just after the engine was started up, but what 
does that signify? Boilers appear to burst just 
as easily and as frequently, too, when the eng'ine 
for which they furnish steam have been running* 
an hour or two, as they do when they are just 
started, and sometimes they explode during* the 
night when no steam is being used, and others ex- 



188 MODERN EXAMINATIONS 

plode when they never were used for supplying 
an engine. 

We are told that electricity accumulates in a 
boiler until it finally gets so full of it that an 
explosion follows, but it appears as if in order to 
hold a large volume of electricity, a boiler would 
of necessity have to be set so that it would be in- 
sulated from all surrounding objects and we 
never saw a boiler set in that way to be used for 
ordinary purposes. We suppose that if a boiler 
were carrying a heavy pressure and should be 
struck by lightning that the concussion together 
with the heavy pressure might cause an explosion, 
but that is a different thing. The favorite cause 
ascribed is that there was not sufficient water in 
the boiler to prevent the catastrophe, for it is 
claimed that the water having got low, the plates 
became red hot, and when cold water was pumped 
in, it immediately flashed into steam, which ac- 
cumulated faster than the safety valve could dis- 
pose of it, hence the trouble. 

The first point that we wish to call attention to 
in this connection is this: "Do the plates of an 
ordinary boiler contain heat enough to cause a 
large body of water to evaporate so rapidly?" Is 
this not worthy of consideration? The second 
point is that in the case of an ordinary tubular 
boiler, the water would have to be very low before 
the plates could get red hot, and if the feed enters 
through the bottom of the shell the boiler would 
have to be entirely empty before cold water could 
be pumped on to the red hot sheets? We do not 
advance the claim nor make the assertion that in- 
sufficiency of water cannot cause a boiler to ex- 
plode, for we believe that it will under certain 
conditions. 

If the iron in a boiler becomes red hot, it is not 



OF STEAM ENGINEERS. 189 

SO strong" as it is when as hot as normal condi- 
tions, while in use make it, and then it might g-ive 
out under .an ordinary working- pressure, but an 
examination of the wreck would surely disclose 
the cause of the disaster. 

Experiments have been made to show the truth 
or falsity of the red hot sheet theory, and in every 
instance where the cold water was pumped on to 
the red hot plates, a very natural result followed, 
and that is that the plates cooled off. The rise in 
pressure was very slight, or else conspicuous on 
account of its absence in every instance. 



190 MODERN EXAMINATIONS 



CHAPTER XIvI. 

STEAM BOII^ER EXPLOSIONS CONTINUED. 

If the plates are allowed to gfet red hot while 
the boiler is under a full working- pressure, and 
they g-ive out on this account, there would be an 
elongation of the iron, or perhaps we oug'ht to 
call it a reduction of the cross section at the 
point of rupture, which would prove, in connec- 
tion w4th the g-eneral appearance of the iron, that 
the plates were red hot if such were the case. 
However, the sheets in a boiler may be ruined by 
low water, without causing- them to g-et red hot, 
for if they are not covered for a short time at 
once, and the practice is persisted in, the streng-th 
of the iron will be lessened, and in time it may be- 
come unable to sustain an ordinary working- 
pressure. 

Many persons appear to think that low water 
is the one and only cause of the explosion of 
steam boilers, and of these we wish to ask a ques- 
tion. Suppose that you have a chain that is cap- 
able of sustaining- a weig'ht of 4000 pounds and no 
more. If you attempt to lift a weig-ht of 6000 
pounds wdth it, as a matter of course one or more 
of the links in it are broken, and the weig-ht is not 
lifted. Now if you had so arrang-ed matters that 
the chain was covered with water when the strain 
was put upon it would it have made it any strong-er 
than when no water was near it? Undoubtedly 
you will reply in the neg-ative, but did you ever 



OF STEAM ENGINEERS. 191 

rei3.ect that if more strain is put upon the iron in 
a boiler than it can stand that it will break in two, 
just the same as the iron in the chain did when it 
was taxed beyond its strength? If a boiler is safe 
at 80 pounds pressure, and you attempt to carry 
150 pounds on it, do not be surprised if the result 
is disastrous, notwithstanding- your boiler is full 
of water, even to its hig-hest part. 

Some people appear to think that if a boiler had 
three g'ag'es of water in it when it exploded, the 
water would all be there afterwards, forg-etting- 
that when the pressure is so suddenly relieved, a 
portion of it will flash into steam and float away. 
On the other hand, those who advocate the idea 
that all of the water will always flash into steam 
under such conditions are not wholly rig-ht, for 
it cannot be converted into steam unless there is 
heat enoug-h stored in it to cause it to evaporate, 
and the necessary heat is not alwa3^s present. 
Some claim that if a boiler does explode when 
there are three g'ag^es of water in it, the result will 
not be disastrous, for as soon as the pressure is 
relieved, the water will simply run out, and that 
is all that there is to it, but while some weak 
boilers may have g'iven out under a low pressure, 
and the result been as above mentioned, still there 
was some special cause for it, and it is the ex- 
ception rather than the rule. 

There are several other theories which have 
been advocated at various times in the past, with 
a greater or less deg-ree of enthusiasm, but which 
have failed to secure recog-nition by theoretical 
and practical steam eng-ineers, and consequently 
have been laid on the shelf. 

The real cause for all boiler explosions is 
simply that the structure was not strong' enoug-h 
to stand the strain put upon it. 



192 MODERN EXAMINATIONS 

Of course we shall proceed to specify the differ- 
ent reasons for this state of things, and call atten- 
tion to some of the practices of boiler makers and 
boiler users, that work together in perfect har- 
mony to bring- about these catastrophes which 
some people think originate in mystery and end 
in uncertainty. 

We saw an article in an alleged funny paper 
some time ago, which deprecated the practice of 
telling what caused a boiler to explode, after it 
had gone up in a cloud of dust, and expressed a 
wish that hereafter we might be informed of the 
dangerous condition of affairs just before the de- 
parture of the source of power, so that we should 
have time to get out of the way. A good sugges- 
tion, truly, but while it is not possible to tell just 
when the last straw wdll be laid on the camel's 
back, still we can point out things that should be 
avoided because they eventually lead to trouble. 

There is great rivalry among boiler makers at 
the present time, as to who can furnish a certain 
plant for the least money, or build a boiler that 
will evaporate more water than any other extant, 
and sometimes it appears as if they w^ere endeavor- 
ing to outdo all others in presenting unique 
designs. 

Some of these are not so planned as to be dur- 
able in practice, although they may show a high 
duty when tested for economy. It is not intended 
to specify any particular kind or style, but some 
of them are so designed that unequal contraction 
and expansion cause more strain on the several 
parts than the steam pressure does, which 
shortens the life of the fabric, and is a defect 
which is apt to cause trouble before it is discov- 
ered in practice. 

The design may be such as to necessitate the 



OF STEAM ENGINEERS. 193 

use of larg"e, flat surfaces, which are alwa^^s to be 
avoided as much as possible, as they are weak 
points and must be strengthened with braces and 
stays, unless said parts are made of cast iron, and 
then it is almost impossible to g'uard against blow 
holes and excessive strains caused by the action 
of the metal itself in cooling after it is cast. If it 
is necessary to cut larg'e holes in the shell, as it is 
with some kinds, it is a source of weakness even 
after the edges have been reinforced by riveting 
cast-iron frames on them. 



194 MODERN EXAMINATIONS 



CHAPTER XLII. 

STEAM BOILER EXPLOSIONS CONCLUDED. 

In some other kinds, series of holes are bored 
in the shell, into which tubes of some kind or de- 
scription are expanded, which, without doubt, 
g-reatly weakens the shell. In others great de- 
pendence is placed on bolts, which are expected to 
hold g-ood sized parts tog'ether against the direct 
pressure of steam, which is also a weak point. 
Still others are so made that parts above the 
water line are exposed to the action of the 
products of combustion on their way to the chim- 
ney, and although it is expected that those 
products will be comparatively cool by the time 
that they reach these exposed parts, still they are 
sometimes hot enough to do much harm. 

Poorly constructed boilers are the cause of 
many explosions, and under this head may be 
mentioned defective riveting, which is probably 
the most difficult fault for the running engineer 
to discover, for boilers have been run for years, 
and passed several inspections by agents of the 
insurance company, by whom they are pronounced 
all rig-ht, and afterwaid, through some mishap, or 
in some accidental way, it has been discovered 
that several rivets in a single seam were defective, 
and undoubtedlv had been so from the time that 
the boiler was built. If the sheets are punched 
or drilled separately it sometimes happens that 
the holes do not come fair when they are put to- 
gether, and to remedy the trouble the drift pin is 



OF STEAM ENGINEERS. 195 

inserted and made to do regular duty, ,the result 
being- that the iibres of the iron are disturbed, 
and sometimes the plate is cracked. In either of 
the above cases the result is that there is a weak 
spot there, and when the wreck is examined after 
the explosion we are told just where the initial 
rupture was. 

In other cases not enough braces are put in to 
make the boiler safe under the pressure that it is 
designed to carr}^ or the}^ I'^^a-v be improperh^ lo- 
cated, so that some of them have more strain on 
them than they can safeh^ carr}^ or one or more 
of them might be defective and break, thus caus- 
ing- an excessive load to be put upon the others, 
causing' them to g*ive out also. Sometimes the 
braces on a flat surface may be in g'ood order and 
properly located at that end of them, but at the 
other end they may be bunched together, which 
concentrates the strain Jn one place more than it 
ought to, and trouble follows. Disastrous ex- 
plosions have been caused by this defective ar- 
rang-ement of these important parts. 

Sometimes braces are made in such a wav that 
when a heavy load is put upon them thev will 
straig'hten out, thus increasing' their length, 
allowing the head to bulg'e out before thev really 
perform the work that they were intended for. 

Some defects in the iron or steel of which the 
plates are made are so well covered up as to escape 
detection until they are put into use, but even if a 
boiler is well designed and properly constructed 
after it has been used for a time it will show signs 
of wear. Some steam users evidently are not 
aware of this fact, for they seem to be of the 
opinion that because a boiler is made of iron or 
steel it can never wear out; but when we consider 
the work that thev h^ive to do, and the influences 



196 MODERN EXAMINATIONS 

that are at work to cause their destruction, 
even when well managed and cared for, it is not 
surprising' that the\^ do not last forever. Take 
for illustration the case of an ordinary tubular 
boiler furnishing' steam for an automatic, non- 
cendensing- eng'ine, developing- 100 horse power. 
Every hour there are 3000 pounds of water 
pumped into this boiler, or 15 tons every ten 
hours. Enoug'h heat must be g'enerated under it 
to evaporate this larg'e amount of water, and of 
course it must pass throug'h the iron before it 
can reach the water. If the plates were always 
clean it would not be so bad, but when a hard 
scale has accumulated on 'hem it requires more 
heat to do the work, as scale is a non-conductor 
of heat, and consequently the life of the iron is 
burned out sooner. The fact that this water cir- 
culates rapidh^ must not be lost sig'ht of, for that 
portion which is directly over the fire rises as it 
becomes heated, and must be replaced by that 
from cooler parts, and this is kept up as long' as 
the boiler is in use. 

It is an old saving' that the "g'entle waves wear 
the solid rock," and will they not wear on iron 
just as well? In manv cases the scale acts as a 
protector, and so is of some value, but neverthe- 
less we notice that the inspectors report some 
cases of internal g'rooving* nearly every month. 
But what do we find where boilers are not used 
in an intelligfent manner? How is it when the fires 
are drawn, the hot water blown out, and the cold 
water immediately run into them? The top is 
covered with brickwork, which retains the heat, 
while the lower part is cooled oif by the water, 
which causes it to contract or shorten, and so it 
is not to be wondered at, when the seams must be 
caulked or the tubes expanded. Even when one 



OF STEAM ENGINEERS. 197 

boiler of a battery is allowed to cool off, and is 
then filled with cold water, and the steam is turned 
into it from the other boilers, the effect is just as 
bad; yet this is often done in some places. In addi- 
tion to all this and more that mig-ht be added, inter- 
nal corrosion is getting- in its work of weakening- 
the shell, heads and tubes, and when at last the 
crystalized plates gfive out, or, in other words, an 
explosion occurs, we are told that the fireman was 
careless and let the water g*et low, or that some 
mysterious ag-ency has been at work which is 
beyond the power of man to control, therefore 
nobody is to blame. 



198 MODERN EXAMINATIONS 



CHAPTER XLIII. 

STEAM PIPE COVERINGS. — COMBUSTION OF FUEL. 

If the question is asked as to what kind of a 
covering- for steam pipes is the most efficient, it 
will be safe to reply that on general principles 
that covering which is the most porous, or in 
other words which allows the greatest quantit}^ of 
air to be confined within its limits, will prove the 
best. As for the need of a covering of an}^ kind 
that has been established by many experiments at 
different times and under various circumstances, 
and while in bare pipes the condensation is some- 
times as great as half a pound of steam per hour 
per square foot of surface exposed, when the 
same pipes have been properly covered, this has 
been reduced to about one-eighth of a pound in 
the same time. Excessive condensation is not 
only expensive, but dangerous in some cases, for 
with high speed engines w^ith small clearance, if 
the steam pipe is long, the water of condensation 
may not do harm of itself, although it will prove 
an annoyance, but if the boilers prime, even 
slightly, the two together may wreck the engine, 
when neither one alone would do it. The porous 
covering must be in turn covered with some sub- 
stance that will not admit air through it, for while 
the air space is well known to be an excellent non- 
conductor of heat, still it must be remembered 
that this must be a dead-air space, for if it can 
circulate around the pipes its efficiency will be 
very low, or perhaps no better than none at all. 



OF STEAM ENGINEERS. 199 

A covering- made of straw, well protected from 
the outside air, has proved very efficient on ac- 
count of the larg-e air space that it formed, while 
a reg-ular air space covering- has proved a failure, 
because the air was allowed to circulate. A test 
was once made on a steam pipe of medium length, 
but which was rather larg-e for the service re- 
quired, to determine how much steam was con- 
densed in its passage to the engine, and it was 
demonstrated that in cool w^eather fully 25 per 
cent, of the steam g-enerated was lost, or con- 
densed before it reached its destination. When 
the pipes were well protected this was reduced to 
about three per cent. Much attention has been 
g-iven to this matter lately, and several first-class 
coverings are in the market, and ma}^ be procured 
at reasonable expense. 

The air that we breathe is composed of ox^^gen 
and nitrogen, and the coal that the engineer is ex- 
pected to make steam with is composed of carbon 
and hydrog-en. We are of the opinion that some 
of the coal that we have to burn contains larg-e 
quantities of other matter, and that some of the 
air that we breathe is diluted with foreign sub- 
stances, but, however, these are the principal in- 
gredients with which we have to deal. When we 
have a good lire in our boiler furnace there is a 
process of rapid oxidation going on which we call 
combustion. To carry out this process the car- 
bon and hydrogen in the fuel combine with the 
ox3^gen in the air, and when we g-et the proper 
combination, or, in other words, the rig-ht quali- 
ties of these tog-ether, the result is perfect 
combustion. When we consider that the air is 
composed of oxygen 21 parts and nitrog-en 79 
parts b}^ volume; or oxygen 77 parts and nitrog-en 
23 parts by weight, and when we consider that the 



200 MODERN EXAMINATIONS 

air that supplies our furnaces is supplied by vol- 
ume, or, in other words, accordino- to the space 
vacated by the products of combustion, we see 
that we must take in much that we do not need, in 
order to g-et what we do want. It is customarv, 
however, to speak cf the number of pounds of air 
that we need to burn a pound of coal, and we are 
told that average coal chemically consumes 10.7 
pounds of air for each pound of combustible, but 
ordinarily a g^reat deal more than this is used, as 
we practicallv never realize such results in prac- 
tice. Again, when we consider that when oxygen 
and hydrogen are present in the right proportions 
for it, they combine to form water, instead of fire, 
and in that case more heat must be taken to evap- 
orate this water, which, of course, is a loss. An- 
other authority tells us that the minimum amount 
of air that will be needed for the best grades of 
coal is 12 pounds of air for each pound of coal as 
we find it, and as each pound of air at a tempera- 
ture of 62° F. occupies 13.14 cubic feet of space, 
we see that each pound of coal needs 13.14x12 = 
157.68 cubic feet of air when burned under the 
most favorable conditions, and these conditions 
are not present in an ordinary boiler furnace. On 
the contrary, many times the conditions are such 
that 24 pounds, or 315.36 cubic feet, are used for 
each pound of coal disposed of. From the above 
it will be seen that if the candidate for a license is 
asked how many pounds of air is disposed of for 
each pound of coal consumed, he should reply: 
"From 12 to 24 pounds, according to conditions." 



OF STEAM ENGINEERS. 201 



CHAPTER XLIV. 

BURSTING PRESSURE OF STEAM BOILERS, THICK 

NESS AND TENSILE STRENGTH OF 

BOILER PLATE. 

In addition to what was said in Chapters 14, 15 
and 16 concerning- the streng-th of a boiler, the 
following- will be found of value to the engineer. 
They were taken from standard works on steam 
eng-ineering-, but as such formula are g-iven 
in a very condensed form, often without ex- 
amples by way of illustration, the averag"e engi- 
neer finds it rather hard work to understand 
them. The author needs no one to tell him this, 
for he knoAvs it b}^ experience, and if he can suc- 
ceed in putting matter in more extended form, so 
that it may be more readily applied by his asso- 
ciates in the profession of steam eng-ineering, one 
of his objects will be accomplished. 

The following are given for determining the 
bursting pressure, thickness of plate, and tensile 
streng-th of plate, respectively : 
4480 / ^^ 



d 

dt> 



4480 6^ 
dp 



=t 



4480 ^^ 
in which /^thickness of plate in decimals of an 



202 MODERN EXAMINATIONS 

inch, ir=tensile streng'th of plate in tons per 
square inch, <f=internal diameter in inches, and 
^=effective or bursting- pressure per square inch. 
For illustration we will assume that we have a 
boiler 60 inches in diameter, made of iron plates 
.375 inch thick, whose tensile stren§*th is 50,000 
pounds per square inch of sectional area, and the 
longitudinal seams are double riveted and possess 
.70 of the streng-th of the solid plate. Applying- 
the first formula we find that 4480 X. 375 = 1680. 
The value of S is to be stated in tons, and in the 
example it is g-iven at 50,000 pounds, therefore to 
reduce it to tons we must divide by the number of 
pounds in an Eng-lish or "long-" ton, and 50,000-^ 
2240=22.32. 1680x22.32=37,497.6. 

In the formula the internal diameter of shell is 
to be taken, which of course is proper, but in the 
case of plates one-half inch thick, or less, it is 
customary to take the outside diameter, as by so 
doing- the matter is much more simple, and the 
difference in the result is small, being but about 
one pound, for a safe working pressure in this 
case: 37497.6^60 = 624.96 pounds, which is the 
value oi p in the formula as applied to this exam- 
ple. This, it must be remembered, is the burst- 
ing pressure of a boiler made without riveted 
seams. As we have assumed that the longitudinal 
seams possess .70 of the strength of solid plate, 
we multiply 624.96 by .70 and our product is 
437.472, and if we use 5 as a factor of safety we 
find that the safe working pressure is 87.5 pounds. 

Referring to the second formula, and substitut- 
ing for the symbols their values as determined 
above, gives us the following: 
60x624.96 

=.375 inch. 

4480x22.32 



OF STEAM ENGINEERS. 203 

which is the thickness of plate. Referring- to the 
third formula, and substituting* for the symbols 
their values, we have 
60x624.96 

=22.32 tons per square inch. 

4480 X. 375 
If we wish to know how far out the centre of the 
heads of this boiler may be bulged without ex- 
ceeding* the elastic limit, or, in other words, how 
far out of truth they may be sprung at the centre 
and still return to their original position when the 
pressure is removed, we may use either of the 
following formula, assuming that there are no 
braces or tubes to hold them in position : 
r d 

— =<^, or — =b 
22 44 

in which r equals radius, d equals diameter and b 
equals bulging pressure. Assuming the heads to 
be of wrought iron one-half inch thick g'ives us 
the following: 

30 60 

— =1.36 inches, or — =1.36 inches. 
22 44 

If we wish to know how much pressure j)er 
square inch it will require to do this, we may use 
the following : 

815/^ 

— — =i> 

d 

in which /= thickness of head in inches, 6-= tensile 
stress of the head in tons per square inch at the 
the elastic limit, <^= diameter of the boiler, and/ = 
pounds per square inch. 

Applying this to the case in hand, and substi- 
tuting for the symbols their values, and our for- 
mula becomes 



204 MODERN EXAMINATIONS 

815 X. OX 11. 16 

=75.8 



60 
pounds. Using- 5 as a factor of safety gives us 
15.16 pounds as the safe working- pressure of 
such a head without braces or sta3^s. An explan-' 
ation of the way that we obtain the value of S in 
this case is in order. As before noted, we take 
tensile streng-th of the iron at 50,000 pounds, or 
22.32 tons, and as the elastic limit is one-half of 
this, we divide 22.32 by 2, and the quotient is 11.16 
tons. As even numbers are often used in these 
calculations, the value of S is taken at 12 tons, 
which is proper here, whence the following- 
formula is derived: 
For an iron head 

/ 
10,000—==^ 

d 
and for a steel head 

11,500—=/ 
d 
in which /= thickness of head in inches, ^=diam- 
eter of the boiler, and /=bulg-ing- pressure in 
pounds per square inch. Making use of the 
former, we have 

.5 
10,000— =83 

60 
pounds bulg-ing- pressure, or 16.6 pounds safe 
working- pressure. This is a trifle more than we 
obtained by a preceding- formula, but this increase 
is due to the fact that elastic limit is taken at 12 
tons, which makes the tensile strength 24 tons or 
53,760 pounds, instead of 50,000 pounds as we as- 
sumed. The terms "pounds" and "tons" are 



OF STEAM ENGINEERS. 205 

both used here in order that the reader may fully 
understand both of them, but we prefer "pounds" 
wherever practicable, as it ag*rees with American 
practice, while the ton is more frequently used by 
the English eng*ineer. 



206 MODERN EXAMINATIONS 



CPAPTER XLV. 

FLAT, CONCAVE AND CONVEX BOILER HEADS. 

If the head of the boiler that we took for illus- 
tration were made of steel instead of iron we 
would use the following- formula: 

t 
11500—=^ 
d 
in which the symbols refer to the same elements 
as in that given for an iron head. Applying* this 
g-ives us 

.5 
11500— =95.45 
60 
pounds, and with a factor of safety of five, the 
result is 19.09 pounds. Suppose that this boiler 
is equipped with a dome 24 inches in diameter, 
and this dome has a cast iron head two inches 
thick. If we wish to know how much this will 
bulg-e at the centre, without exceeding- the elastic 
limit, we can use the following- formula to deter- 
mine it : 

d 

— =B 
44 
and when we wish to determine the pressure that 
will do this we use the following-: 

t 
4000— =j6 
d 
In which <:/= diameter of head, 3 = deflection at 



OF STEAM ENGINEERS. 207 

the centre, within the elastic limit, /^thickness of 
head in inches, and ^= pressure in pounds per 
square inch. Applying- these we have 
24 " 2 

— =.545 inch, and 4000— =332 
44 24 

pounds bulging* pressure, or 66.4 pounds safe 
working" pressure. According' to the above this 
head is much weaker than other parts of the 
boiler, but there are several thing's to be taken 
in consideration which effect the result. The 
formula is based on the assumption that cast iron 
has an elastic streng-th of five tons per square 
inch of sectional area, as being* an averag^e, but 
while some very poor specimens have shown even 
less streng-th than this, other g-ood specimens 
possess double this streng-th, and exceptionally 
g-ood ones have demonstrated that it requires 17 
tons to break them, which w^ould make the allow- 
able pressure more than three times that g-iven by 
the formula. 

Remelting' the iron improves its quality, and 
without doubt none but the very best cast iron 
that can be procured should ever be used in 
boiler construction. This material possesses 
but very little elasticity, so that the tensile 
strength is but little more than the elastic 
strength. Usually the steam nozzle is cast on the 
dome head, and while the hole tends to make the 
part w^eak, still the raised portion of the nozzle 
reinforces it, and in a g'reat measure counteracts 
its bad effects. If it is necessary to drill holes in 
such heads to make minor steam connections they 
should be located as far apart as possible. 

The foreg-oing- formulas refer to flat heads, and 
ordinarily these are what the eng-ineer has to deal 
with, but it may be well for him to understand 



208 MODERN EXAMINATIONS 

how to calculate the pressure that a spherical 
head will stand, or in other words a head made in 
convex form, or in the engineer's vernacular, "a 
bulg-ed head." Such a head cannot very well be 
used for a tube sheet on a boiler, but there are 
other places where such heads are used. Their 
streng-th may be determined by use of this 
formula 

8960 t s 



V 

in which ^=pressure in pounds per square inch, 
^'=thickness of the head in inches, ^= elastic 
streng-th of head in tons per square inch, r= 
radius of the head, and ^'= versed sign or rise of 
the head in inches. 

Assuming- elements of the preceding- case, 
except that the head is bulg"ed out six inches at 
the centre and made spherical in form by the 
boiler makers, instead of being- flat, and substi- 
tuting for the symbols their values, our formula 
becomes 

8960 X. 5x11. 16 

-:320 

30^' 



6 

pounds, elastic limit, or 64 pounds safe working 
pressure. 

Having explained the way to read many of the 
formula which appear in the preceding' chapters 
of this book, I have considered it necessary to ex- 
plain those in this chapter further than to give 
the figures which illustrate their application, but 



OF STEAM ENGINEERS. 209 

as the one just g-iven looks rather formidable, a 
full explanation may be advisable. 

The number 8%0 is to be multiplied by the 
thickness of the head in inches or parts of an 
inch, and the product by the elastic strength in 
tons per square inch, and this we may term our 
first product. The radius, or one-half of the 
diameter of the head is to be multiplied by itself 
and the product divided b}^ the rise of the head in 
inches. To this quotient add the rise of the head 
and the sum will be our second product. Divide 
the first by the second and the quotient will be the 
elastic limit in pounds per square inch. 

Thus we see that by giving' the head a 
spherical form, the rise of the segment being six 
inches, we have increased the safe working press- 
ure from 15.16 pounds in the flat head to 64 
pounds in the spherical one. A careful study of 
these formulas will show that in calculating' the 
safe working' pressure of the shell, the ultimate 
tensile strength of the iron is used, while for the 
heads the elastic strength is taken, but if we wish 
to make a comparison of the strength of the shell 
of a boiler, made without seam or weld, and of a 
spherical head, we must take the same quantity 
for both, which ma}^ be stated at 24 tons tensile 
strength. 

In this case both shell and head must be of the 
same thickness in order to make the comparison 
proper. If a 60-inch boiler shell is made of iron 
one-half inch thick we find that it will take 4480 X 
.5x24-^60=8% pounds to burst it, and if the 
head is spherical, the rise of it being eight inches, 
it will require 8960 X .5x24= 107520; 30x30^8+8 
= 120.5; 107520^120.5=892 pounds to rupture it, 
therefore if the rise of the spherical head is made 
one-eighth of the diameter of the shell, or one- 



210 MODERN EXAMINATIONS 

fourth of its radius, approximately, both head 
and shell will possess equal streng-th. Care 
should be taken to avoid confounding- the tensile 
streng-th of the iron in these calculations with its 
elastic limit. 

A careful study of these problems will show 
that, if the wrought iron head of a plain cylinder 
boiler should be made concave, it would be much 
strong'er than either a flat or a convex one, for 
the reason that the pressure tends to compress 
the iron, and the same authority that tells us that 
the ultimate tensile streng-th of iron in tension is 
about 24 tons, also tells us that "the resistance 
to compression is an indefinite quantity." 

From this it would appear to the casual reader 
that the streng'th of a concave head is so g-reat as 
to be almost unknown, but when we consider that 
the concave head will not retain its form under 
great pressure, and if it did, it would bring- an 
excesive stress to bear on that part of the shell 
which immediately surrounds it, we see that there 
are modifying* conditions present. 



OF STEAM ENGINEERS. 211 



CHAPTER XLVI. 

WROUGHT IRON, STEEL AND CAST IRON BOILER 

HEADS. 

It may be well to give a separate formula to de- 
termine the elastic limit of streng'th of spherical 
boiler heads when made of wroug'ht iron, steel or 
cast iron. They are as follows : 
108,000 t 



V 

for a wroug-ht iron head. 

125,000 / 
=p 

+v 

V 

*^or a steel head, and 

45,000 
=p 

+v 

for a cast iron head. In the above formulas the 
elastic limit of the metal is taken at 12 tons for 
wroug'ht iron, 14 tons for steel and 5 tons for 
cast iron, and the explanation found in Chapter 45 
will apply here. In the 60 inch wroug'ht iron 
boiler that we have taken for illustration in work- 



212 MODERN EXAMINATIONS 

ing out and applying" these rules and formula 
there are some flat surfaces which will need to be 
braced, as for instance the heads above and below 
the tubes, and when these are not strengfthened 
except b}^ the braces, the following- formula may 
be safely used : 

407 / ^^ 

=p 

a 
in which / = thickness of the plate in inches, .9 = 
strengfth of the plate in tons per square inch at 
the elastic limit, ^ = maximum elastic pressure in 
pounds per square inch, and <f= clear distance 
apart of the braces. By the latter is meant the 
distance from the outside of one brace to the out- 
side of another, and not from centre to centre, as 
for instance if a section of plate is laid out in 
squares and braces one inch in diameter are gfiven 
a pitch of eig'ht inches, or it is eight inches from 
centre to centre of them, then the clear distance 
apart is seven inches. 

If the plate is not laid out in squares, but in 
rectang'les or irreg'ular forms, then the g'reatest 
clear distance apart must be taken for the calcula- 
tion, in order to be on the safe side. Let us apply 
this formula to the boiler head taken for illustra- 
tion, which is one-half inch thick, and assume that 
the braces are placed in squares eig-ht inches from 
centre to centre, making* the value of d seven 
inches. It will be remembered that we have taken 
the value of S at 11.16 tons for a reason already 
explained. Our formula thus becomes 
407 X. 5x11. 16 

=324. 437 

7 
pounds pressure at the elastic limit. If we adopt 
a factor of safetv of 5, we find that our safe work- 



OF STEAM ENGINEERS. 213 

ing- pressure is 64.887 pounds. We shall show 
presently how this head is to be made strong- 
enough to stand a higher pressuse than this, and 
at the same time would state that we are well 
aware that it is not practical to lay out this seg-- 
ment of a boiler head in equal shares of eigfht 
inches, but the reader can readily see how these 
rules can be applied to the water leg^s of locomo- 
tive and marine boilers or for any similar work. 

If we already have the values of -p, t and s, and 
wish to determine the value of d^ our formulr 
becomes 

407 / 5 
=d 



and its application 

407 X. 5x11.16 



7 inches. 



324.437 
If we already have the values of /, d and s, and 
wish to ascertain the value of /, the formula 
becomes 

f d 

407 6^ 
and its application 

324.437x7 

-=.5 inch. 

407x11.16 

If we already have the values of 7*), d and t, and 
wise to ascertain the value of s, the formula 
becomes 

f d 

=^ 

407/ 
and its application 



214 MODERN EXAMINATIONS 

324.437x7 

== 11.16 tons. 



407 X. 5 
If the valve of ^ is taken at 12 tons, we may use 
the following-, which are somewhat shorter: 

5000 t ^ d 5000 t 

=^. =/. ^d, 

d 5000 ^ 

If the head is made of steel we may take the 
value of s at 14 tons per square inch, and the fol- 
lowing- may be used 

5700/ fd 5700/ 

=^. = t. = d. 

d 5700 f 

But even after we have figured out all of the above 
examples, it does not tell us whether the brace is 
strong- enoug-h to withstand the strain that will 
come upon it when our boiler is put into service, 
and for this purpose we must use the following- 
formula, remembering- that the maximum elastic 
pressure is taken at 324.437 pounds, or rather it 
was so determined by one of the foreg-oing* rules, 
and it may be well to remind the reader that this 
formula is to determine the diameter of a brace 
that will stand just the same pressure that the 
plate will, under like conditions: 

PP' p 

.024 j/ =^ 

S 
In which P= pitch of stays or braces between 
centres longitudinally, or in other words length- 
wise, P' = pitch of braces, transversely or cross- 
wise, ^ = maximum elastic pressure in pounds per 
square inch, 6^ = elastic strength or iron in the 
braces, in tons per square inch, which must cor- 
respond to the elastic strength of the plate, and 



OF STEAM ENGINEERS. 215 

^= diameter of brace. Our first business is to 
make the reading- of the formula plain, and it is as 
follows: Multiph^ P. P' and/ tog-ether and divide 
the product obtained by S. 

Ascertain the square root of the quotient and 
multiply it by .024; substituting- for the symbols 
their values the formula becomes 
.024 v'SxSx 324.437 

_ — =1 inch 

11.16 
which corresponds to the diameter assumed in 
order to illustrate preceding- formulas. 

Ag-ain, when the value of S is taken at 12 tons, 
the formula becomes .0069 \/P P ^=d, and if ,5 is 
equal to 14 tons, as in the case of steel being- used, 
it is .0064 ^P P' jy=d. 

If the brace of stay bolt has a thread cut on it, 
the diameter must be taken at the base of the 
thread. 



216 MODERN EXAMINATIONS 



CHAPTER XLVII. 

BRACING STEAM BOILER HEADS. 

It now becomes necessary for us to g^ive the 
heads of this boiler a little more attention, in 
order to determine how we may make that por- 
tion of them which is above the tubes strong 
enough to be safe under the working* pressure of 
87.5 pounds, for we have demonstrated that even 
with braces placed eig-ht inches apart the heads 
are only fitted to carry about 65 pounds, and as it 
is not practical to have so many as this arrang-e- 
ment calls for we must resort to some other 
means for stiffening" this important part, until it 
will be perfectly safe under the working- pressure 
that we have adopted. The shape of the part to 
be braced is in the form of the segfment of a circle, 
'and the first question to be settled is as to what 
portion of this seg'ment is already stiffened by the 
flang-e of the head and by the tubes. 

If we were to provide braces for the w^hole of 
this part of the head above the tubes, we should 
be on the safe side, and many authorities on this 
subject evidently intend for this to be done, as 
they ig-nore the matter altog'ether, while others 
simply state that the flang'e imparts streng^th to an 
arbitrary number of inches from the diameter of 
it, as was done in Chapter 16 of this book, 
which statement was intended to be on the safe 
side, but a rule will now be g^iven which may be 
applied to any boiler, and which we shall show is 



OF STEAM ENGINEERS. 217 

based on correct principles. The distance that 
the flange imparts streng^th to is due to the thick- 
ness of the head, and as a matter of course, to the 
pressure to be carried, and these points are also 
what determines the pitch of the stays or braces, 
and as we have not yet shown what this pitch 
would be in the case that we have assumed, we 
will now do so. 

Our safe working pressure is 87.5 pounds and 
factor of safety, 5, therefore the pressure which 
equals the elastic limit is 87.5x5=437.5 pounds. 
The safe working' pressure for the shell is based 
on the tensile streng-th, but the safe working- 
pressure of the head is based on the elastic limit. 
Applying- a formula already g-iven to determine 
the clear distance apart of the stays we find that 
407 X. 5X11. 16 

=5.19 inches. 

437.5 
or 6.19 from centre to centre, which we will call 6 
for convenience sake, as it will not materially alter 
the result. This means that each stay will sup- 
port the pressure on a space of six inches square, 
or in other words if we marked a space six inches 
square and put the stay in the center of it, the 
plate will be well supported to this extent. This 
being- the case we may safely regard the fasten- 
ings of the head to the shell as a stay which is 
able to support a space of three inches wide each 
side of it, or in other words, the diameter of the 
circle to be braced will thus be reduced by three 
inches on each side, or six inches in all. From 
the above we derive the following formula for the 
distance supported by the flange: 

407/5 

f-B=^ 



P 2 



218 MODERN EXAMINATIONS 

in which /f= thickness of the plate, ^= strength of 
plate at elastic limit in tons per square inch, P= 
maximum elastic pressure in pounds per square 
inch, B= one-half diameter of brace and ^= dis- 
tance from circumference. Applying* this to our 
our boiler, we find that 

407 X .5 X 11.16= 2271.060 ; 437.5 X 2 =875 ; 2271.060 
^875=2.59+.5=3.09 inches. We may also re- 
gard the top row of tubes as braces, and as we 
have seen that the plate is strengthened for a dis- 
tance of three inches from the centre of brace, or 
2.5 inches from the outside of it, so we safely 
assume that a space 2/^ inches wide above the 
upper row of tubes is provided for by the tubes. 

The outside diameter of our boiler is 60 inches, 
therefore the head is 59 inches in diameter and 
the distance from the centre of it to the upper 
part of the shell is 29.5 inches. If we locate the 
upper row of tubes five inches above centre of 
head, and allow 2.5 inches more for strength im- 
parted by the tubes, we find that the base of 
segment will be 7.5 inches above the centre of 
circle, and subtracting six from 59 for reasons 
already explained, the radius of the circle, which 
is to form the arc of the segment is found to be 
26.5 inches, and this is the surface which must be 
held by braces. 

In other words, draw a circle 53 inches in diam- 
eter, and then divide it into two unequal parts by 
a straight line 7.5 inches drawn above the centre of 
it. The smaller part represents the area to be 
braced, and in order to reduce the number of 
braces necessary, we will rivet on pieces of T iron, 
and while these are often placed radially, we pro- 
pose to locate them in a horizontal position, and 
calculate their strength in this position, in order 
to illustrate a plan that is sometimes adopted in 



OF STEAM ENGINEERS. 219 

such cases. These irons will be considered as 
flang'ed beams of unsymmetrical proportions, and 
their streng'th given accordingdy. It will also be 
necessary to ascertain the exact area of the space 
to be braced, and multiply it by the pressure to be 
carried, that we may know how much of a load to 
provide for. There are a variety of rules for this 
purpose, some of which require the use of a table 
to use them, but we will illustrate one which any 
eng^ineer can use at his discretion, the only arti- 
cles necessary being* a clean spot on the eng-ine 
room floor on which to draw a circle, a wire nail 
for the centre of it, a piece of wire with a loop at 
each end of it of a proper leng-th to represent the 
radius of the circle, a pencil, a straig-ht-edg-ed 
ruler and a pair of compasses. 

Having" drawn the circle and laid out the seg'- 
ment, we will proceed in our next chapter to ascer- 
tain the area of it. 



220 



MODERN EXAMINATIONS 



CHAPTER XLVIII. 

AREA OF SEGMENTS OF CIRCLES. 

Rule to determine the area of the segment of a 
circle when it is less than a semi-circle — Multiply 
one-half of the arc by the radius of the circle, and 
call the result the first product. Multiply one- 
half the leng-th of the chord by the distance from 




the centre of the circle to the centre of the chord, 
and call the result the second product. From the 
first product subtract the second and the remain- 
der will be the area of the seg-ment. A few words 
by way of explanation of terms used may not be 



3 



OF STEAM ENGINEERS. 



221 



out of place. Segment means a part cut off or 
divided, so in this case it means a part of a circle. 
Arc is a contraction of the word arch, and as used 
here it refers to the curved line which forms the 
upper part of the segment. 

The chord is the straight line which forms the 
remainder of the segment, and connects the two 
ends of the arc. To illustrate the foregoing rule 
and apply to the case in hand we refer to Pig. 10, 
which is a circle supposed to be 53 inches in diam- 
eter, the upper part of which is the segment that 
we wish to ascertain the area of. The chord is 
drawn 7 1-2 inches above the centre for reasons 
already explained. The distance from 1 to 4 is 

Fi<s 11 




34 7-32ds or 34.21875 inches, and the radius, or 
one-half of the diameter of the circle, is 26.5 
inches; 34.21875 X26.5 = 906.79 square inches, 
which is our first product. The distance from 1 
to 2 is 25 3-8 or 25.375 inches, and from 2 to 5 is 



222 MODERN EXAMINATIONS 

7.5 inches; 25.375x7.5=190.31 square inches, 
which is our second product; 906.79 — 190.31^ 
716.48 square inches, which is the area of the 
segment. 

While we are on the subject we will g-ive a rule 
for determining- the area of a segment of a circle 
— when it is larger than a semi-circle. 

Multiply one-half the length of the arc by the 
radius of the circle and call the result the first 
product. Multiply one-half the length of the 
chord by the distance from centre of circle to 
centre of chord and call the result the second 
product, Add the two products and their sum 
w^ill be the area of the segment. To illustrate we 
refer to Pig*. 11, which represents a circle 53 
inches in diameter, and the upper or larger part 
of it is the segment that we desire to know the 
area of. This corresponds to the lower part of 
Fig\ 10. Applying the rule we find that the dis- 
tance from 1 to 4 is 49 7-32ds or 49.21875 inches. 

The radius of the circle is 26.5 inches, and 
49.21875x26.5 = 1304.29 square inches, which is 
our first product. The distance from 1 to 2 is 
25 3-8 or 25.375 inches, and from 2 to 5 it is 7.5 
inches; 25.375 X 7. 5:= 190. 31 square inches; 1304.29 
+190.31 = 1494.6 square inches, which is the area 
of the segment. If we add the two areas together 
we will have the area of the whole circle, it is evi- 
dent, and 716.48+1494.6=2211.08 square inches. 
If we desire to get the area of the whole circle di- 
rectlv we would have squared the diameter and 
multiplied by .7854, and 53 X 53 X. 7854 =2206. 18, 
and as the result obtained indirectly varies but 
4.9 square inches from this, the difference is small 
when we consider the total number of inches con- 
cerned in the calculation. 

In measuring* the distances on curved lines it is 



OF STEAM ENGINEERS. 223 

well to take the dividers or compasses to do it 
with, as accuracy is thus secured, and would also 
suggest that the whole of the arc be measured and 
the sum divided by two rather than to draw a ver- 
tical line from the centre of the chord to centre 
of arc, or to w^hat is supposed to be the centre, 
for unless very great care is exercised an error 
will be introduced here. As we have demon- 
strated, the area above tubes to be strengthened 
by tee irons and braces contains 716.48 square 
inches, and as we proposed to carry 87.5 pounds 
on each square inch, 716.48x87.5=62,692 pounds 
to be supported. 

If we were to put in braces of round iron 1 1-8 
inches in diameter, allowing 6000 pounds to each 
square inch of sectional area in the brace, we 
should have 62,692-^6000 = 10.4, or, say 11 braces. 
As we have 716.48 square inches to stipport and 11 
braces to do it with, to ascertain the number of 
square inches each one would be called upon to 
support, we may divide 716.48 by 11, and our 
answer is 65.13, the square root of which is 8.062, 
or practically the space supported by each brace 
will be 8 inches square. But, as before stated, 
we do not propose to put in so many braces, but 
will introduce tee irons laid horizontally, and first 
we will consider them as being* supported at the 
ends only, although there are conditions present 
which modify this, and which tend to make the 
structure stronger than ever. 

This head will support a light pressure without 
either braces or tee irons, but this fact is usually 
ignored in such calculations, and as it is an error 
on the safe side, if an error at all, it is not to be 
condemned. The radius of this head is 29.5 
inches, but as it is supported for a distance of 
7 1-2 inches above the centre bv the tubes and for 



224 MODERN EXAMINATIONS 

a distance of three inches from the shell by the 
flang-e, the height that we have to provide for is 
reduced to 19 inches, and we propose to use tee 
iron of a uniform thickness of one-half inch and a 
depth of four inches, or in other words 4x|-inch 
tee irons. 



OF STEAM ENGINEERS. 



235 



CHAPTER XLIX. 

STRENGTH OF TEE IRONS. 

In calculating* the strength of tee irons, there 
are several points to be taken into consideration, 
and, in fact, it is a subject that bristles with 
points. To begin at the foundation of the matter 
we refer the reader to Fig. 12. It represents a 



B. 






hi 


kl 



piece of iron one-half inch thick, and 3% inches 
wide. It rests upon the blocks A A at each end, 
and supports the weight B laid upon its centre. 
In Pig. 13we* haVe a piece of iron one-half inch 
thick and four inches wide. 



226 



MODERN EXAMINATIONS 



It also rests upon blocks C C at each end, 
while the weight D is laid upon its centre. The 
point we wish to illustrate by these fig-ures is that 
the iron that is set up edgewise in Fig*. 12 will 
support a much greater weight at its centre than 
will the iron which is laid down flatwise, as in Pig. 
13, even if they were both the same size. The 
comparative strength of irons used in this way 
has been determined by experiment and found to 
be as 1 is to 1.73. In these calculations the iron 
shown in Pig'. 12 will be referred to as the web, 
and that in Fig. 13 as the flange, therefore if the 
strength of the flang-e be taken as 1 then the 
strength of the web wnll be 1.73, for if the flange 
will support 1000 pounds, then the web will 
support 1.73x1000=1730 pounds. 

Again referring to Fig. 12 we find that when 
the weight is put upon it the lower part has to 
withstand a direct pull, or in other words is in 
tension, while the upper part of it is pressed 



rio.i5. 




together, or is in compression. There is a point 
in this bar of iron that is neither in tension nor 
compression, and as the bar is the same size 
throughout, or in other words is symmetrical in 
section, this point is found to be at the centre of 



OF STEAM ENGINEERS. 



227 



the bar, measured vertically, and is called its 
neutral axis. If one edg-e of this bar of iron were 
to be made thicker than the other, then the 
neutral axis will not be at the centre, but will be 
moved toward the thickest edge, therefore when 
we put the two bars of iron shown in Pig-s. 12 and 
13 together we have a piece of tee iron, the width 
of both flange and web being four inches, when 
considered singly, and their thickness, one-half 
inch, or in other words w^e have a tee iron four by 
one-half inches shown in section in Pig. 14. 

The reader will notice at once that the neutral 
axis of this iron is much below its centre, as the 



F16.1+. 



lower edge is thicker than the upper, but how 
much below the centre is the next problem to be 
solved, and for this purpose we refer the reader 
to Pig. 15. B}^ extending the web down across 
the flange, as shown by the dotted lines at E E, 
we have a space, or part of the flang-e, at either 
end, which is 1.75 inches long, and it is these parts 



228 



MODERN EXAMINATIONS 



which we must reduce to their equivalent in the 
web, and, as before stated, the difference between 
them is as 1 is to 1.73; therefore it becomes a 
problem in proportion, for 1.73:1 : : 1.75:1, or in 
short, 1.75^1.73=1, which is the required dis- 
tance in inches. So we draw the dotted line at F 
P, showing- the reduction in the flange. 

As this flang-e is all in tension, the question 
naturally arises as to why it is not proper to take 
the whole of it into consideration, but it should 







FiG.15. 


1 i 




k 1 



be remembered that the flange if taken by itself 
will bend much easier than the web, and as the tee 
iron must remain rig'id, it is necessary to make 
this reduction to show its equivalent to the web. 
In other words that part of the flang-e which is 
between the dotted line P P if set up edg-ewise 
would be equivalent to the whole flange taken as 
it is. The next step is to ascertain the centre of 
g-ravity for the web above the flange, and also for 
the reduced section of the flange. This is done 



OF STEAM ENGINEERS. 



229 



as shown in Pig. 16. For the web it is at G, and 
for the flang-e at H. We will now draw a line 
across the top, as shown at I I, which we will call 
a datum line, because from it we must take some 
measurements. 

Ficlfe 




The next step is to ascertain the areas of the 
web and flang-e, respectively, and multiply them 
by the distance of their centres of gravity from 
the datum line. The area of the web is 3.5x.5= 
1.75 square inches, and its centre of gravity is 1.75 
inches from the datum line; 1.75x1.75=3.06. 
The area of the flange is 2. 5 X. 5^1. 25 square 



230 MODERN EXAMINATIONS 

inches, and its centre of gravity is 3.75 inches 
from the datum line; 1.24x3.75=4.68. These 
two results are to be added tog-ether and 3.06 + 
4.68=7.74, which is to be divided by the sum of 
the areas of the web and flang-e, and 1.75+1.25^3 ; 
7.74-^3=2.58 inches, which is the distance of the 
neutral axis of the complete four-inch tee iron 
from the datum line. This axis is shown by the 
line J J and must be considered as a fixed point, 
from w^hich other measurements are to be taken 
and other calculations made, the first of which is 
to determine the tensile resistance of that por- 
tion of the four inch tee iron which is below the 
neutral axis, but from the foregoing* it is plain 
that the reduced section of the flang-e must be 
taken, instead of its whole section. 

A moment's consideration will also show us 
that as the neutral axis is to be reg-arded as a fixed 
point, that portion of the iron which is directly be- 
neath it, say the first quarter-inch in depth, is not 
so effective as the lowest quarter-inch of the web, 
or of a like amount of iron at the extreme lower 
part of the flang-e, for in a certain sense this tee 
iron, Fig-. 16, may be regarded as a lever of the 
first kind, in which the neutral axis J J repre- 
sents the fulcrum, the datum line I I the weight 
to be raised, and the lower part of the flange is 
where the power is applied. By this illustration 
it will be seen that a square inch of the iron at the 
lower part of the flange is more effective than a 
square inch immediately under the neutral axis, 
and also that each square inch of iron or fraction 
thereof, is effective according- to its distance from 
the fulcrum, that is the natural axis. We will 
divide the part in tension into sections and mul- 
tiply the area of each section by the distance from 
the centre of it to the neutral axis. 



OF STEAM ENGINEERS. 



231 



CHAPTER L. 

COMPRESSIVE AND TENSILE STRENGTH OF SEC- 
TIONS OF TEE IRONS. 

In Fig". 17 we have the reduced section of the 
four-inch tee iron, divided into small sections, 
each one quarter of an inch wide beg-inning- at the 

Fig. 17. 



I 


L 


I 


J 




J 




















: . K : 





bottom and extending- up to the neutral axis. The 
lower one has an area of 2.5 X. 25 = . 625 square 
inch, the next one above it is the same, the next is 



232 MODERN EXAMINATIONS 

. 25 X. 5 =.125 square inch, the next is the same, 
and also the next, but the one next to the neutral 
axis is smaller, being* .17x.5=.085 square inch. 
Their respective distances from their centres to 
the neutral axis are, first, 1.295 inches; second, 
1.045 inches; third, .795 inch; fourth, .545 inch; 
fifth, .295 inch; sixth, .085 inch. 

Multiplying- these together as described in the 
closing paragraph of Chapter 49, we have 

.625x1.295 = .809 

.625x1.045 =.653 

.125X .795 = .099 

.125 X .545 =.068 

.125 X .295=. 036 

.085 X .085 =.007 
These products are to be added together, and 
their sum is 1.672, which is to be divided by the 
distance from the neutral axis to the extreme 
lower part of section, which in this case is 4—2.58 
= 1.42 inches, and 1.672^-1.42=1.17. This quo- 
tient is to be multiplied by the constant number 
1.73, and the product by the total tensile strength 
of the iron per square inch, which we assume at 
50,000 pounds. 1.17 X 1.73 X50, 000= 101,205 pounds 
which is the strength of the section below the 
neutral axis. Not the strength per square inch, 
but the total strength, as we have already taken 
into account the area. 

We must next locate the centre of the tensile 
stress of this four-inch tee iron, which is the cen- 
tre of tensile stress of the reduced section shown 
in Fig. 17, or rather that part of it which is below 
the neutral axis J. J. To do this we must multi- 
ply the area of each strip by the square of the dis- 
tance from its centre to its neutral axis. Add 
these products together and divide the sum so ob- 
tained by the sum of the first products (in this 



OF STEAM ENGINEERS. 233 

case 1.672 inches), and the quotient will be the dis- 
tance from the neutral axis to the centre of the 
tensile stress. The first or lower one has an arc 
of .625 square inch, and its distance is 1.295 inch, 
therefore in carrying* out the above directions we 
have .625X1.295X1.295=1.048. In treating- the 
second one the same way we have .625 X 1.045 X 
1.045=. 682. In the case of the third it is .125x 
.795 X. 795 =.079. The fourth g-ives us .125X.545 
X.545 = .037. The fifth is . 125 X. 295 X. 295 = .010, 
and the sixth .085 X .085 X .085 = .0006. Add these 
products tog-ether and their sum is 1.8566. The 
sum of the first products is 1.672, therefore 1.8566 
-f-1. 672 = 1.11 inches, which is the distance from 
the neutral axis to the centre of the tensile stress. 
See the point K in Fig-. 17. 

Our next move is to find the centre of the com- 
pressive resistance, namely of that portion of the 
web which is above the neutral axis J. J. The 
same process which we used to find the centre of 
the tensile stress K may also be used here, but as 
this part is a rectangfle we know that this point is 
at two-thirds of its heig-ht, and two-thirds of 2.58 
inches is 1.72 inches, therefore the centre of the 
compressive resistance is 1.72 inches above the 
neutral axis See point L, Pig-. 17. If for any 
reason it is desired to find the total compressive 
resistance (which is not required in this case), it 
must be remembered that while according- to a 
g-eneral law the tensile and compressive resistance 
is the same in a section which is symmetrical, still 
in one which is not symmetrical, as in this case, 
the compressive resistance is greater in direct 
proportion or ratio, as the diiference in the dis- 
tance from the neutral axis to the centres of each 
resistance. Here it would be 1.11 : 1 : : 1.72 : 1.55» 
the latter denoting- the excess of streng-th of the 



234 MODERN EXAMINATIONS 

compressive resistance, owing- to its g'reater dis- 
tance from the neutral axis. All that concerns 
this example in this connection is to see that the 
part in compression is strong- enough to prevent 
buckling- when the stress is put upon it, and as we 
have shown that the compressive streng-th is 1.55 
times the tensile streng-th this point is well 
covered. 

We have refrained from g-iving- any rule or for- 
mula for determining- the f oreg-oing- points in this 
calculation, as they would necessitate the use of 
many words and phrases w^hich would need ex- 
planation, in following- out our plan of endeavor- 
ing* to make each point clear as we proceed, so 
that we have deemed an illustration of the way to 
proceed to be sufficient, as it can be applied to any 
beam of similar section by substituting- the proper 
sizes. We now g-ive a g-eneral f ormvila, in contin- 
uing- the f oreg-oing- illustration: 
S4D 
■ =W 

Iv 

in which S = total tensile resistance of the section 
below the neutral axis under g-iven conditions in 
pounds, D=the vertical distance apart of the cen- 
tres of tension and compression in inches, Iv^the 
span in inches, and W = the breaking- weig-ht in 
pounds. 

If the value of W is required in tons, then the 
value of S must be stated in tons. Substituting* 
for the symbols their values our formula becomes 

101205x4x2.83 

= 95470 pounds. 

12 



OF STEAM ENGINEERS. 235 



CHAPTER LI. 

CALCULATING THE LOAD ON TEE IRONS. 

In illustrating- the use of the preceding* formula 
we have explained the way to determine the value 
of all the factors except that of L, which we have 
stated as being- 12. It is now in order to tell how 
that is obtained, and for this purpose we will re- 
fer the reader to Fig. 18. The outside circle in 
full lines represents the head of the boiler that 
we have under consideration, which is 59 inches in 
diameter. The circle in dotted lines represents 
that part of the head which is supported by the 
flang-e, and its diameter is 53 inches. The dotted 
line M represents the top of the upper row of 
tubes, and is five inches above the centre of the 
circle. 

The N represents a tee iron four inches wide. 
It is located five inches above the upper row of 
tubes, because the tubes are assumed to impart 
stiffness to 2/^ inches of the head above them, and 
the tee iron will consequently stiffen another 
space 2>2 inches wide, and this five-inch space is 
well within the limits of what the head will safely 
bear of its own thickness, as previously explained. 
The O represents another space five inches wide, 
and P is another four-inch tee iron, while Q is a 
space 2}4 inches wide, which is supported b}'^ the 
tee iron. By adding- tog-ether the above, it will be 
seen that w^hile the radius of this circle is 26.5 
inches, 25.5 inches are here provided for, leaving 
a small segment only one inch in height out of the 



236 MODERN EXAMINATIONS 

calculation, but as its area is small, and our factor 
of safety in calculating- on the other elements is 
larg-e, this will not materially affect the result. 

Let us now see how much pressure the tee iron 
N will be called upon to support. By drawing* a 
line throug-h its centre extending* from side to 
side of the circle represented by the dotted lines, 
we find that the averag*e leng*th of this line is 47.5 
inches, which we will call 48 inches for convenience 
in calculating*. The space that it has to support 
is nine inches wide, as already explained, there- 
fore 48x9 = 433 square inches, and as we are to 
carry 87.5 pounds pressure, 432x87.5=37,800 
pounds. We will make our braces of round iron 

F«6 18 





.^^ 


^=o>'-^^ 


^ 




^^ 


p 


l^v 


// 




o 


^>s 


ff 




H 


n 


1 

C- 



n 



/> 



1^ inches in diameter, the area of which is 1.767 
square inches, and as we are not to exceed a pull 
of 6000 pounds per square inch on our braces, 
1.767x6000 = 10,602 pounds, which is the limit for 
each brace; 37,800^10,602=3.56, so that we shall 



OF STEAM ENGINEERS. 237 

need four braces. By ptittingf one brace six inches 
each side of the centre of this iron, and another 
one 12 inches from each of these, we find that they 
are evenly distributed, and that the g-reatest span 
or distance between supports is 12 inches. This 
is how we determined the value of Iv in the 
formula. 

In putting- in these braces it would be well to 
run the two nearest the centre from head to head, 
and the two outside ones from head to shell. In 
determining- the space to be supported by the 
upper tee iron, we find that its averagfe length is 
about 32.25 inches. By locating* one brace in the 
centre of this iron, and one each side of it at a 
distance of 11 inches, our load will be properly 
distributed, and as the span here is less than in 
the case of the lower one, w^e are on the safe side. 
As the space to be supported by the tee iron is 
32.25 inches long* and 9 inches wade, it contains 
290.25 square inches, and the total pressure on it 
is 25,396 pounds. As each brace is safe under a 
pull of more than 10,000 pounds, the marg-in is 
larg-e enoug-h to cover every conting-ency. 

As shown in Chapter 50, this span of 12 inches 
has an ultimate streng-th of 95,470 pounds. Tak- 
ing* one-half of this as the elastic limit, and using* 
a factor of safety of -^\e, as before, we find the 
safe load to be 9547 pounds. Let us see whether 
our working- load exceeds this or not. The span 
is 12 inches long-, and it supports a space nine 
inches wide; 9x12 = 108 square inches, and multi- 
plying* by the pressure gives us 108x87.5=9450, 
which is a trifle less than the safe load. With the 
upper tee iron the working* load will be less than 
this, showing* that we are still on the safe side. 

If the lower row of tubes are so low down that 
only a hand hole can be put in each head, below 



238 MODERN EXAMINATIONS 

the tubes, then no braces will be needed here, but 
if a manhole is put in the front head, then braces 
will be needed according' to conditions, but usu- 
ally two are enough, and they should extend from 
head to head, as it is poor practice to rivet a brace 
to the shell directly over the fire, 

It may be the opinion of some readers that such 
a boiler is safe under a much higher pressure than 
this, and their opinion may be based on the fact 
that they know of similar boilers that are doing 
it, but what does that signify? A certain gentle- 
man wanted to hire a coachman, and advertising 
the fact, was soon called upon by several appli- 
cants for the position. He submitted to each 
one in turn the following question: '* Suppose 
that I eng'ag'e you to drive for me, and while 
riding with my wife and family we should come 
to the vicinity of a precipice. How near could 
you drive to the edge of it and escape accident?" 

The first one said that he could approach within 
a yard of it and get away safely. He was told that 
if his services were required he would be notified. 
The second one said that he could drive within a 
foot of it and yet be safe. He received the same 
reply as the first one. The third one said that he 
was such a complete master of his business that 
he could cause the carriage wheels to roll within 
one inch of the edge and still not go over it. He 
received the same reply as his predecessors. The 
fourth one said that he would keep just as far 
away from it as circumstances would allow. He 
was engaged at once. 



OF STEAM ENGINEERS. 239 



CHAPTER LII. 

SAFE WORKING AND COLLAPSING PRESSURE OF 
TUBES AND FLUES. 

In some of the works on steam boilers there is 
very little said concerning* the collapsing- pressure 
of tubes and flues. This may be partly accounted 
for by the fact that in the ordinary tubular 
boiler, with three or four-inch tubes, the col- 
lapsing- pressure of them is so much g-reater than 
the bursting" pressure of the shell and heads, that 
they (the tubes) are practically out of the ques- 
tion. As an illustration of the truth of the above 
statement, we introduce the following- formula: 
4480 S T 
=P 

D 

in which S = collapsing- pressure in tons per square 
inch of section of metal, T— thickness of tube in 
inches and D = the external diameter in inches. 
The vakie of S is obtained by the following' rule: 
Prom 25 subtract 2| times the diameter of the 
tube. For a 3 inch tube it will be 2f X3=8 and 
25—8 = 17 tons. For a 4 inch tube it will be 2f X 
4 = 10.64 and 25-10.64 = 14.36 tons. 

We will apply this to the case of a 4 inch tube 
.125 inch thick and when we have substituted for 
the symbols their values, our formula becomes 

4480 X 14. 36 X. 125 

= 2010 



240 MODERN EXAMINATIONS 

pounds collapsing* pressure. Or the following 
may be used as it is at times more convenient. 
112,000 

T 12,000=P 

D 
By this we mean that if 112,000 is divided by the 
diameter of the tube and 12,000 subtracted from 
the quotient, then by multiplying* the remainder 
by the thickness of the tube, the product will be 
the collapsing- presure in pounds. Applying- this 
to the four inch tube as before we have 
112,000 

.125X 12,000=2000 

4 
pounds collapsing- pressure. This is practically 
the same as with the preceding- formula. Using- 
a factor of safety of 10, which corresponds to a 
factor of five when based on the elastic limit, the 
safe working* pressure of this tube is 200 pounds, 
and if it were a three-inch tube it would be 316 
pounds. The foreg-oing* rules apply to small 
round tubes not more than 18 feet long-, but not 
to large flues. 

The United States Treasury rules for finding 
the strength of lap-welded flues, when the diam- 
eter is not less than seven inches or more than 16 
inches, may be expressed by the following form- 
ula: 

T4400 

= P 

R 
in w^hich T=thickness of flue, R = radius of flue in 
inches, and P = the pressure that may safely be 
carried. This, however, is subject to modifica- 
tions, one of w^hich is that the leng-th must not ex- 
ceed 18 feet, for when they are longer than this a 
reduction in the pressure carried must be made 



OF STEAM ENGINEERS. 241 

amounting- to three pounds for each foot or frac- 
tion thereof over 18 feet. When the pressure is 
between 60 and 120 pounds, the flue must be made 
in lengths not to exceed five feet, and riveted to- 
g-ether in a substantial manner, or corrug-ated, the 
effect of which is practically the same. If the flue 
is more than 16 inches and less than 40 inches in 
diameter, the same formula may be used, except 
that instead of using- the constant number 4400 we 
must substitute the number 2840. 

Applying- the formula to a flue 14 inches in diam- 
eter and one-quarter of an inch thick, and substi- 
tuting* for the symbols their values, our formula 
becomes 

.25x4400 

=157 pounds 

7 

for a leng-th of 18 feet or less, but if it were 22 
feet long-, the pressure would be 157 — 12 = 145 
pounds. 

Applying- the latter to a flue 24 inches in diam- 
eter, less than 18 feet long-, and three-eighths of 
an inch thick, the pressure would be 

.375x2840 

=88.7 pounds. 

12 

The rule given by the same authority to determine 
the thickness of a flue for a given pressure, is ex- 
pressed by the following formula: 

RP 

=T 

4400 

the letters denoting the same factors as in the two 
previous ones. 

Applying this to thel4-inch flue we have 



242 MODERN EXAMINATIONS 

7x157 

=.25 inch. 

4400 
Previous to 1892 the United States Treasury rules 
specified that the flues of a boiler should be made 
in lengths not exceeding three feet, in which case 
the following applies : 

89,600 T^ 

=P 

LD 
in which T=thickness, Iv=length of sections in 
feet, D = diameter in inches, and P = safe working 
pressure. Applying this to our 14-inch flue, our 
formula becomes 

89600 X. 25 X. 25 

=133 pounds. 

3X14 
Thus it will be seen that every part of this boiler 
is abundantly able to withstand the pressure to be 
put upon it, for the shell has a large margin, the 
braces are not overloaded, neither are they spaced 
so far apart as to introduce an element of danger, 
and even if flues are put into it instead of tubes, it 
is still safe under the designated pressure. 



OF STEAM ENGINEERS. 243 



CHAPTER LIII. 

CONCLUSION. 

We have now arrived at the conckiding* chapter 
of this book, in which we have called attention to 
calculations that engineers are supposed to under- 
stand when they aspire to positions in places 
where a strict license law is in force. Occasion- 
ally we meet a man who claims that all of the du- 
ties of an engineer can be learned in a month. If 
we were to proceed to argue the case, we might be 
tempted to assert that possibly that portion of 
the business that he is familiar with could be 
learned within the specified time, but such argu- 
ments are not always profitable. 

It is the author's experience that those engi- 
neers who study the most are the ones who are 
willing to allow that there is much more for them 
to learn, while oftentimes those who never spend 
any money or time in getting posted in the theo- 
retical part of their business are the ones who 
claim to know it all. The author is willing to ad- 
mit that the more a man studies steam engineering 
the more he will feel that there is more beyond, 
and that it is better further on, and this, too, after 
having spent several years in patient study, re- 
search and endeavors to improve every oppor- 
tunity to gain knowledge on the subject. 

It was our privilege some time ago to visit a 
panorama representing one of the greatest battle- 
fields known to history. At the entrance we pur- 
chased a key explaining the entire view in detail. 



244 MODERN EXAMINATIONS 

but at first we were contented to gaze at the grand 
spectacle as a whole. Soon tiring* of this we were 
about to depart, but opening- the key and looking 
up the meaning of one part after another, and 
calling to mind the facts that they pictured to us, 
we soon found that, together with a friend, we 
were intensely interested, and when more than 
two hours had passed away, we had mastered only 
a portion of what was before us, but could not 
stay longer at that time. Shortly afterward, 
while conversing with a person who lived in that 
vicinity, we spoke of the grandeur of the sight, 
and of the wide extent of its teachings, but were 
coolly informed that it could all be understood in 
15 minutes time. 

So it is with some men in charge of steam 
plants, for they understand only what may be 
termed the superficial part of the business in 
which they are engaged, and consequently think 
that it can all be learned in a few weeks, but 
when they get a key to it (and we believe this to 
be a proper term, for it unlocks one of the doors 
to the storehouse of knowledge) and make use of 
it, they soon discover their mistake. It has been 
one of the objects of the author to make every 
subject treated of as plain as possible, and to in- 
troduce only those rules and formulas which are 
sanctioned by good authorities and that are based 
on common sense. 



OF STEAM ENGINEERS. 245 



I IN D E X 

TO 

300 EXAMINATION 

Questions and Answers 



(The number after each question denotes the number of the page on which 
the answer to the question will be found.: 



1. What is lap ? 28 

2. What is lead ? 29 

3. What is clearance ? 119 

4. Explain how to set valves ? 29 

5. Explain how to reverse an engine ? 30 

6. Which travels the farthest, the crank pin or 

wrist pin ? 32 

7. What is an eccentric ? 32 

8. How do you find the throw of an eccentric?. . 32 

9. Does it change the throw of it to reduce its 

outside diameter ? 33 

10. How do you determine the proper size of steam 

pipe? ,. . .34-172 

11. How do you determine the proper size of ex- 

haust pipe? 34 

12. How do you determine the proper size of steam 

ports? 35 



^46 MODERN EXAMINATIONS 

13. How do you determine the proper size of ex- 

haust ports? 35 

14. What should be diameter of crank shaft?. . . .36-180 

15. What should be the diameter crank pin? ^6 

16. What should be the diameter of wrist pin?. ... $6 

17. What should be the diameter of connecting 

rod? ^6 

18. How long should the connecting rod be to give 

good results. ^6 

19. How large should the piston rod be? 37 

20. . What should be the length of the main bear- 

ing? 37 

21. How would you determine the length of the 

eccentric rod ? 37 

22. How would you determine the length of the 

valve rod ? , 37 

23. What is the counterbore? . . . 37 

24. What is the counterbore for? 37 

25. What is the difference between a non-condens- 

ing and a condensing engine? 39 

26. What is the forward pressure?. . 39 

27. What is the back pressure? 39 

28. What is the mean effective pressure? 39-106 

29. What is the back pressure absolute? 40 

30. What is the initial pressure? 40 

31. What is the terminal pressure? 40 

32. What is a throttling engine? 40 

^;^. What is an automatic engine? 40 

34. What is an adjustable cut-off engine? 40 

35. What is a compound engine? 40 

36. What is a compound condensing engine? 40 



OF STEAM ENGINEERS. 247 

37. What is a triple expansion engine? 40 

38. What is a triple expansion condensing engine? 40 

39. What is a quadruple expansion engine? 41 

40. What is a quadruple expansion condensing en- 

gine ? 41 

41. What are the advantages and the disadv^antages 

of the before mentioned types? 41 

42. What is a horse power? 45 

43. How do you determine the horse power of an 

engine? 45 

44. How do you find the area of a circle? 48 

45. State how to determine the speed of engine, 

the size of cylinder, mean effective pressure 
and horse power being given? 49 

46. State how to determine the diameter of the 

piston of an engine, the stroke, revolutions, 
mean effective pressure and horse power be- 
ing given? 49 

47. How do you find the square root of a number? 50 

48. How would you determine the necessary mean 

effective pressure to do a certain amount of 
work, all other data being given? 54 

49. How do you find the horse power constant?. . 54 

50. How would you increase the mean effective 

pressure of an engine? 54 

51. Is there any other way of increasing the power 

of an engine ? 55 

52. How would you determine the speed that an 

engine is intended to run at? 56 

53. . How would you determine the proper size of 

governor pulle}^ ? 57 

54. Explain how to figure speed of shafting? 58 

55. How would you determine the mean effective 

pressure of an engine without an indicator? 60 



248 MODERN EXAMINATIONS 

56. What is the ratio of expansion? 60 

57. What are hyperbolic logarithms? 61 

58. How would you tell whether the valves and 

piston are tight or not? 62 

5.9. What is a crank ? 62 

60. What is meant by the valve gear of an engine 63 

61. How do you ascertain the necessary weight for 

the rim of a flywheel? 64 

62. How is the constant whole number 7,000,000 

obtained ? 66 

6;^. What is a flywheel for? 64 

64. Give the formula for obtaining the weight of 

the entire wheel? 66 

65. What is the safe limit of speed for flywheels?. . 68 

66. How do you determine the percentage of gain 

in pressure due to adding a condenser?. ... 70 

67. If a condenser is added how much can we re- 

duce the boiler pressure and keep the point 
of cut-off and mean effective pressure con- 
stant? 70 

68. What is the theoretical saving by adding a con- 

denser? 71 

69. How would you determine the point of cut-off 

to give a certain mean effective pressure?. . 71 

70. How would you prove this rule? 72 

71. How would you determine the safe working 

pressure of a boiler?. 74 

72. What is meant by the pitch of the rivets? 79 

73. How Avould you determine the strength of a 

section of solid plate? 79 

74. How do you determine the strength of net 

sections of plate? 80 

75. How do you calculate the strength of rivets in 

a joint? 80 



OF STEAM ENGINEERS. 249 

76. How do you calculate the strength of a double 

welt butt joint? 81 

77. What part of the ordinary tubular boiler is 

usually calculated to be the weakest?. 83 

78. Is it a good plan to have braces extend from 

head to head ? 83 

79. Give the reasons? 8;^ 

80. Why are pieces of T iron riveted to boiler 

heads? 85 

81. How much stress is usually allowed for braces 

in boilers per square inch of sectional area? 83 

82. How W(3uld you determine the safe load for a 

round brace i 1-2 inches in diameter? 84 

83. How do you determine the number of braces 

necessary for a flat surface? 84 

84. Is the stress on a brace extending from head to 

head greater than if it was only from head 

to shell? 85 

85. Is it a good plan to brace from head to shell on 

the lower part of a tubular boiler? 85 

86. Why not? 85 

87. Which makes the strongest joints, punched or 

drilled holes? 85 

88. Give the reason why? 85 

89. Is it necessary to calculate on the whole surface 

of a head exposed to pressure, when laying 
out braces for it? 85 

90. How do you determine the horse power of a 

boiler? 87 

91. How many square feet of grate surface should 

be allowed per square foot of heating sur- 
face ? 88 

92. How do you find the heating surface of a 

boiler? 88 



250 MODERN EXAMINATIONS 

93. What is the water space of a boiler, and how- 

do you ascertain it? 89 

94. How would you reduce it to gallons? 89 

95. How would you determine the weight of the 

water in it? 89 

96. How do you determine the cubical contents of 

the steam space? 89 

97. What is meant by the term "foaming," and 

what causes it? 89 

98. What is meant by priming? 89 

99. What is a separator? 90 

100. How would you determine the proper size of 

safety valve for a boiler? 91 

loi. How would you determine the area of opening 
of a safety valve v^ith a seat beveled at an 
angle of 45 degrees? 93 

102. How would you determine the area, if the angle 

were greater or less than 45 degrees? 93 

103. How would you determine the area of opening 

of a flat valve and seat? 93 

104. Give an example illustrating the above rules?. . 95 

105. What is the difference in the area of opening, 

between a valve with a seat beveled at an 
angle of 45 degrees and one with a flat seat? 96 

106. How would you determine the proper size of 

pump for a steam plant? 96 

107. Hov/ do you calculate the contents of the water 

cylinder of a pump ? 97 

108. Is the capacity of an injector increased by sup- 

plying it with water under pressure? 98 

109. Can hot water be lifted as cold water is? 98 

no. Will an injector take hot water like a pump?. . 98 
III. What is the difference between a hot water 

and cold water pump? 98 



OF STEAM ENGINEERS. 251 

112 How high can a pump raise cold water by suc- 
tion? 98 

113. How hot can water be heated by exhaust steam? 99 

114. How do you calculate the saving made by heat- 

ing the feed water? 99 

115. How would you test the temperature of feed 

water? 100 

116. What is the difference between natural and 

forced draught? 100 

117. Which is the most economical? loi 

118. How would you determine the area of a chim- 

ney for a steam plant ? loi 

119. What is a steam engine indicator? 103 

120. What are its principle uses? 104 

121. How does it show the difference in the load on 

an engine? 104 

122. Name the lines or parts of an indicator card?. . 104 

123. How do you locate the line of perfect vacuum? 104 

124 Is there any way to determine the pressure of 

the atmosphere from height about sea level? 105 

125. How do you locate the atmospheric line? 104 

126. Explain the way to lay out the theoretical ex- 

pansion line? 108 

T27. How do you determine the M. E. P. by the 

planimeter ? iii 

128. Is it possible to calculate the water consump- 

tion from the card ? iii 

129. Does the amount so obtained agree with the 

amount actually used? 112 

130. Give reasons for the discrepancy? 112 

131. Explain the theory of calculating the water 

consumption from the card? 113 

132. Give an example and explain it in detail? 113 



252 MODERN EXAMINATIONS 

133. How do you determine the volume of steam 

used by an engine in a given time? 115 

134. Give a formula which takes into account the 

saving by compression? 117 

135. Illustrate a way to change common fractions 

into decimals ? 75 

136. How do you ascertain the portion of the return 

stroke uncompleted at compression? 119 

137. Give formula for determining water consump- 

tion from pressure at cut-off? 119 

138. Is the percentage of clearance the same when 

taking volume at cut-off as when taking it at 
release? 122 

139. Can the rate of water consumption be obtained 

directly from the card without knowing the 
horse power developed? 122 

140. When so obtained, how do you find the total 

accounted for? 123 

141. Give another rule for calculating the water 

consumption? 124 

142. Give an example illustrating the rule as applied 

to an ordinary card? 124 

143. What difference does it make if the terminal 

pressure exceeds the compression? 126 

144. How does this rule work if the release pressure 

is below the atmosphere? 129 

145. If the release pressure is below the atmospheric 

pressure, what is the effect of opening the 
exhaust valve before the completion of the 
stroke ? 129 

146. In this case what shall we do with the compres- 

sion line? 129 

147. If the water rate is high, is it always due to the 

engine itself ? 131 

148. Why is it better to have an engine under-loaded 

than over-loaded? 131 



OF STEAM ENGINEERS. 253 

149. Give a rule for calculating the water rate in 

the case of a compound engine 131 

150. For what purpose are these rules useful? 132 

151. If the diagram shows a higher terminal pressure 

than it should, where would you look for the 
trouble ? 133 

152. Explain the meaning of the term "re-evapora- 

tion ?" 133 

153. What is meant by initial cylinder condensation? 133 

154. What causes it? 133 

155. If the actual expansion line is below the theo- 

retical one, where would you look for the 
trouble ? 134 

156. If a steam engine is in an exposed place in cold 

weather and the cylinder is not properly cov- 
ered, what is the effect? 134 

157. What will cause the expansion line to rise sud- 

denly? 134 

158. If the expansion line falls suddenly, where would 

you expect to find the cause of it? 135 

159. If the counter pressure line rises suddenly, where 

would you look for the cause of it? 135 

160. Does excessive compression affect the economy 

of an engine? 135 

161. Is it dangerous? 135 

162. Can you give a rule for the amount of compres- 

sion to be given that will apply in all cases? 136 

163. What general rule applies? 136 

164. How can we determine the power developed by 

direct steam and expansion? 13'/ 

165. How do we know that the steam does. work after 

the cut-off has taken place? 137 

166. How can we shorten up this calculation? 138 

167. Give a rule for determining the work done dur- 

ing expansion ? 138 



254 MODERN EXAMINATIONS 

i68. Are the terms "work done" and "power de- 
veloped" interchangeable? 138 

169. Do such rules take account of clearance and com- 

pression? . 138 

170. Are the pressures used in such calculations abso- 

lute? 138 

171. How would you prove the above mentioned 

rules ? 138 

172. What pressure should we carry on our boiler to 

insure the best economy with an automatic 
engine? 139 

173. Does this apply to underloaded engines? 139 

174. Does it apply equally well to a compound con- 

densing engine? 141 

175. What is the effect in a simple non-condensing 

engine if we lower the boiler pressure? 141 

176. What effect does it have in a compound condens- 

ing engine? 141 

177. How does the indicator assist us in deciding on 

the economy of the compound condensing 
engine? 142 

178. If we lessen the difference between the initial 

and the terminal pressures, what is the re- 
sult? 143 

179. Does it increase the efficiency of the compound 

engine to add a condenser? 143 

180. Give the reason for it? 143 

181. What are the comparative sizes of cylinders in 

ordinary practice for this style of engine?. . . . 144 

182. Does the indicator card enable us to determine 

the amount of water needed for the con- 
denser ? 145 

183. Give a formula for determining the volume of 

circulating water needed 145 

184. What does the volume mean in this connection? 146 



OF STEAM ENGINEERS. 255 

185. Is it a good plan to use a feed water heater with 

a surface condenser? 146 

186. What effect does the condenser have on the 

temperature of the feed water? 146 

187. Give reasons for it 146 

188. Give an illustration from practice of the applica- 

tion of this formula 146 

189. Flow do you determine the power developed by 

the compound engine? 148 

190. If a simple engine is overloaded, will it pay to 

add a low pressure cylinder? 150 

191. Give formula for amount of water needed to run 

a jet condenser 151 

192. Illustrate and explain the use of the same? 152 

193. Give formula for use when temperature of steam 

is given instead of its pressure 152 

194. How shall we determine the area of injection 

pipe? 152 

195. What is the meaning of the term "density of 

steam?" 153 

196. If density is given, how would you determine 

the weight? 154 

197. How do you change the vacuum in inches to 

pounds? 155 

198. How do you determine the flow of water in feet 

per second due to a stated vacuum? 155 

199. Does it make a difference whether the injection 

water is above or below the condenser? 156 

200. Is the formula an inflexible one? 156 

201. Does the quality of the injection water affect the 

result ? 156 

202. What precautions should be taken when indicat- 

ing an engine ? 157 

203. Is a knowledge of the indicator of value to the 

running engineer? 157 



256 MODERN EXAMINATIONS 

204. Name the systems in use for heating buildings.. 159 

205. Describe them in detail 159 

206. Why is the use of a fan recommended? 160 

207. Can the water of condensation be returned with- 

out a pump? 161 

208. Explain the principle cause of the failure of 

water to return? 161 

209. In how many ways may systems of direct radia- 

tion be piped? 163 

210. Describe them 163 

211. Which is the best?. . , 164 

212. What are the objections to the others? 164 

213. How should globe valves be connected? 165 

214. Give a rule for determining the radiating surface 

necessary to heat a room 167 

215. What objections are there to the use of this rule? 168 

216. Give a rule that takes into account all of the 

conditions 168 

217. Give a rule for reducing Avail surface to its 

equivalent in glass surface 168 

218. Give an illustration of the way to estimate the 

heating surface necessary for a building. ... 172 

219. Give a rule for determining the area of a main 

steam pipe 172 

220. Give another rule for the same purpose 173 

221. About how much direct heating surface of a 

boiler will be needed for a given case? 173 

222. Does it pay to use exhaust steam for heating 

purposes? 175 

223. How would you estimate the cost of it? 175 

224. Does it necessarily cause excessive back press- 

ure on an engine to use the exhaust for this 
purpose? 175 



OF STEAM ENGINEERS. 257 

225. Give a formula for determining the diameter of 

wrought iron mill shafting to transmit a given 
amount of power 178 

226. If the diameter and speed are given, how would 

you determine the power that it will transmit? 179 

227. Give a formula for determining the diameter of 

steel shafting 179 

228. If the diameter and speed are given, how would 

you determine the power that it will transmit? 180 

229. Give a formula for determining the diameter of 

cast iron shafting 180 

230. If the diameter and speed are given, how would 

you determine the power that it will transmit? 180 

231. Do these rules apply to crank shafts of steam 

engines ? 180 

232. Can you give a formula that does apply to them? 181 

2;^^. Give an illustration of the working of this 

formula 181 

234. Can you give a rule that will determine the 

power that a belt will transmit? 183 

235. What is the safe working strength of leather 

belting? 183 

236. What is meant by the term "half angle of con- 

tract ?" 184 

237. Why is it not taken at 90 degrees? 184 

238. Give a formula for determining the breadth of 

belt to transmit a given horse power. ...... 184 

239. To what kind of belts do these formula apply?. . 185 

240. Mention conditions that will modify them 185 

241. What theories are advanced to account for boiler 

explosions? 186 

242. Explain the superheated water theory 186 

243. Can electricity accumulate in an ordinary boiler? 188 



258 MODERN EXAMINATIONS 

244. What is the effect of pumping cold water on to 

red hot boiler plates? 189 

245. What is the effect of heating boiler plates red 

hot? 188 

246. If a boiler fails on account of the plates being 

red hot, will an examination of the wreck dis- 
close the fact? 189 

247. What will be the appearance of the iron after a 

rupture from this cause? 190 

248. What becomes of the water in a boiler when it 

explodes? 191 

249. Because a boiler shows a high duty when tested 

does it prove that it is a good one to pur- 
chase? 192 

250. What effect does it have on the shell of a boiler 

to bore holes in it and expand tubes or pipes 
into them? 194 

251. What is the effect of defective riveting? 194 

252. Of the use of the drift pin? 194 

253. Of an insufficient number of braces?. 195 

254. Of improperly located braces? 195 

255. Of improperly constructed braces? 195 

256. Will a boiler wear out the same as any other 

structure? 195 

257. What is the effect of blowing off a boiler and 

immediately refilling it with cold water?. ... 196 

258. What kind of covering is the best for steam 

pipes ? 198 

259. How much steam may be condensed in un- 

covered pipes? 198 

260. Why is excessive condensation a detriment?. . . . 198 

261. What is air composed of? 199 

262. What is combustion? 199 



OF STEAM ENGINEERS. 259 

263. How is this process carried on? 199 

264. What is the minimum amount of air required to 

burn a pound of coal?. . 200 

265. About how much is needed under average con- 

ditions? 200 

266. Give a formula to determine the bursting press- 

ure of a boiler 201 

267. For the necessary thickness of the shell 201 

268. For strength of plates 201 

269. If the strength of boiler plate is stated in pounds, 

how would you reduce it to tons? 202 

270. Give a formula for determining the distance that 

a boiler head may be bulged without exceed- 
ing the elastic limit 203 

271. Give a rule for calculating this pressure if the 

head is of wrought iron 203 

272. Also for a steel head 204 

273. Why is it preferable to use the term "pounds" 

in these calculations, rather than "tons?". . . . 205 

274. Give a rule for determining the bulging pressure 

of a cast iron head 206 

275. How does the elastic limit of cast iron compare 

with its tensile strength? 207 

276. How do you calculate the elastic limit of spher- 

ical boiler heads? 208 

277. What must the rise of a spherical head be to 

make it as strong as the shell is when both are 
of the same thickness and made of the same 
material? 209 

278. Is a concave head stronger than a flat one?. ... 210 

279. Why?....... 210 

280. State the conditions which modify the strength 

of concave heads? 210 



260 MODERN EXAMINATIONS 

281. Give a rule for determining the proper distance 

apart of braces or stays in a boiler 212 

282. What is meant by ''clear distance apart" of 

braces or stays in a boiler? 212 

283. Give a rule for determining the pressure that a 

flat head will safely carry 212 

284. For the proper thickness of a flat head 213 

285. Illustrate the difference between a steel head and 

one of wrought iron in this connection?. ... 214 

286. Give a rule for determining the diameter of a 

brace that will safely withstand the same 
pressure that the flat surface of the head will. 214 

287. In the case of a threaded stay bolt, how shall we 

calculate the diameter? 215 

288. Give a rule for ascertaining the distance on a 

head which is supported by the flange 217 

289. To what extent do tubes impart stiffness to the 

head of a boiler? 218 

290. How would you reduce the number of braces 

necessary for a boiler head not otherwise 
supported ? 218 

291. What is meant by the "segment of a circle?". . 221 

292. How would you determine the area of a segment 

that is less than a semi-circle? 221 

293. When it is greater than a semi-circle? 222 

294. Explain and illustrate the way to calculate the 

strength of tee irons 225 

295. What is the neutral axis of a piece of tee iron? 227 

296. Are braces required below the tubes? 238 

297. As boilers are usually constructed, which is the 

strongest, the shell or the tubes? 239 

298. Give rules for calculating the collapsing pressure 

of tubes 239 

299. For the safe working pressure of flues 240 

300. Give a rule for determining the thickness of 

flues, to withstand a given pressure 242 



OF STEAM ENGINEERS. 



261 



I N D B X. 



?^'o. of Question. Page. 



Absolute pressure used 170. 

Adjustable cut-off engine 34. 

Air, composition of 261 . 

Air required to burn a pound of coal. . . . 264, 

Angle of contact 236 , 

Area of circle 44 , 

Area of opening of safety valve 

101-102-103-104-105 , 

Area of chimney 118 

Area of injection pipe 194 

Area of main steam pipe 10-219-220 

Atmosphere, pressure of 124 

Atmospheric line 125 

Automatic engine -^^ 

Automatic engine, pressure for best econ- 
omy 172 

Axis, neutral 295 



34- 



40 
199 
200 
184 

48 

93 

lOI 

152 
-172 

105 

104 

40 



227 



Back pressure 27-29 

Back pressure, caused by heating building .224 

Bearing, main 20 

Belt, breadth of for given horse power. ... 238 

Belt, power that it will transmit 234 

Belt, safe working strength of 235 



39-40 
•175 
• 37 
.184 
.183 
.18-. 



262 MODERN EXAMINATIONS 

No. of Question. Page. 

Blowing off boilers 257 196 

Boiler, direct heating surface of 221 173 

Boiler, explosions, cause of 241 191 

Boiler, heads, tee irons riveted to 80 85 

Boiler, heads, pressure necessary to bulge 

271—272—274. .203-206 

Boiler, heads, elastic limit of 270 203 

Boiler, heads, elastic limit of, spherical. . 276 208 

Boiler, heads, concave 278-279-280 210 

Boiler, heads, difference between iron and 

steel 285 214 

Boiler, heads, supported by flange 288 217 

Boiler, heads, tubes impart stiffness to. . . . 289 218 

Boiler, horse power of 90 87 

Boiler, plates 269 202 

Boiler, plates, effect of pumxping cold water 

on 244 189 

Boiler, plates, effect of heating red hot .... 245 188 

Boiler, plates, failure of red hot 246 189 

Boiler, pressure for best economy 172 139 

Boiler, pressure, effect of lowering. ... 175-176 141 

Boiler, safe working pressure of . 71 . . . 74-202 

Boiler, shell, effect of boring holes in. . , . 250 194 

Boiler, shell, necessary thickness of 267 201 

Braces below tubes 296 237 

Braces, diameter of 286 214 

Braces for part of head exposed to pressure 89 85 

Braces from head to head 78-85-86. . . .83-85 

Braces, insufficient number of . 253. ..... 195 

Braces, improperly located . . 254 195 

Braces, improperly constructed 255 195 

Braces, necessary for fiat surface . St, 84 

Braces, proper distance apart 281 213 

Braces, safe load for 82 84 



OF STEAM ENGINEERS. 263 

'^(^- (if Question. Page. 

Braces, stress on 84 85 

Braces, stress allowed on 81 83 

Bursting pressure of boilers 266 201 

Building, necessary heating surface for. . 218 167 

Building, systems for heating. ... ; 204 159 



Cast iron shafting, diameter of 229 180 

Cast iron shafting, power it will transmit 230 180 

Cast iron, elastic limit of 275 207 

Cast iron head, bulging pressure of 274 206 

Chimney, area of 118 loi 

Circle, area of 44 48 

Circle, segment of a. 291-292—293 220 

Circulating water needed 183 145 

Clearance 3-169. . . .29-119-138 

Coal, air to burn one pound of 264-265 200 

Collapsing pressure of tubes 298 239 

Compression, effect of excessive 160 135 

Compression, line 146 129 

Compression, rule for 162-163 136 

Compression, return stroke uncompleted at 136 119 

Compression, saving by 1 34 117 

Common fractions 135 75 

Compound engine 35-189. . .40-148 

Compound engine, water rate for 149 131 

Combustion 262 199 

Constant, horse power. 49 54 

Connecting rod, diameter of 17 2>^ 

Connecting rod, length of 18 36 

Condensing engine 25-36-38-40. . . . 39-41 

Condenser, theoretical saving by adding a. . 68 71 

Condenser, water needed for a 182-191 . . 145-15 1 



264 



MODERN EXAMINATIONS 



No. of Question 

Condenser, percentage of gain by adding. . 66 

Condenser, surface 185 

Condensation, water of 207 

Condensation in steam pipes 260 

Consumption of water 128 

Counter pressure line 159 

Counterbore 23-24 

Covering for steam pipes 258 

Crank 59 

Crank pin 6 

Crank pin, diameter of 15 

Crank shafts 231-232-233 

Crank shafts, diameter of 14 

Cut-off, consumption of water at 137 

Cut-off engine 34 

Cut-off to give mean effective pressure. . . . 69 

Cylinder condensation 153 

Cylinder, comparative sizes for compound 

engine 181 

Cylinder, effect of not covering 156 

Cylinder, low pressure 190 



Page. 

70 
146 
161 
198 
113 
135 

37 
198 

63 

Z^ 

36 

180 

36 

119 

40 

71 

^Z3 

143 
134 

150 



Defective riveting 251 194 

Density of steam 195-196 153 

Diagram, too high terminal pressure on. . . . 151 133 

Diameter of crank shafts 14-231 . . .36-180 

Direct heating surface 221 173 

Direct radiation 209-210— 211 163 

Double welt butt joint 76 81 

Drilled holes 87 85 

Drift pin 252 194 



I 



OF STEAM ENGINEERS. 



265 



^o. of Question 

Eccentric 7-8 

Eccentric, effect of reducing diameter of . . 9 

Eccentric rod, length of 21 

Elastic limit of boiler heads. . 270-271-272-276 

Elastic limit of cast iron 275 

Electricity, accumulation of 243 

Engine, adjustable cut-off 34 

Engine, automatic t,2> 

Engine, compound 35-189 

Engine, compound condensing 36-1 76-1 77-1 79 

Engine, compound, water rate of 149 

Engine, compound, to determine power of 189 

Engine, crank shafts of 14-231-232-233 

Engine, diameter of piston for 46 

Engine, horse power of 43 

Engine, indicator 119 

Engine, in exposed place 156 

Engine, precautions when indicating 202 

Engine, quadruple expansion 39 

Engine, quadruple expansion condensing. . 40 

Engine, speed of 45-52 

Engine, steam used by in a given time. ... 133 

Engine, to reverse an 5 

Engine, throttling 32 

Engine, triple expansion 37 

Engine, triple expansion condensing 38 

Engine, to increase mean effective press- 
ure of 50 

Engine, to determine mean effective press- . 

ure of 55 

Engine, underloaded and overloaded 148 

Exhaust pipe, proper size of 11 

Exhaust ports, proper size of 13 



Page. 

■ ■ 32 
• • 33 

■ ' 31 
03-208 

. . 207 
. .188 
. . 40 
. . 40 
40-48 
40-141 

131 

148 

36-180 

49 

45 

103 

134 

157 
41 
41 
49-56 

115 
30 
40 
40 
40 

54 

60 

131 

34 

35 



266 MODERN EXAMINATIONS 

No. of Question. Page. 
Exhaust steam for heating. . 113-222-223-224. . .99-175 

Exhaust valve 145 129 

Expansion line 157-158. . 134-135 

Expansion line, theoretical 126 108 

Expansion, ratio of 56 61 

Expansion, work done by 164-167 137 

Explosions, theories advanced to account 

for , 241 191 



Feed water, to calculate saving by heating 114 99 

Feed water, temperature of 115-186-187. .100-146 

Flat surfaces, braces for 83 84 

Flat surfaces, to determine safe pressure. . 283. .203-212 
Flat heads, to determine proper thickness 

of 284 213 

Flow of water 198 155 

Flues, safe working pressure of 299 241 

Flues, thickness of 300 241 

Fly wheels 61-62-63-64-65 64 

Foaming, cause of 97 89 

Forced draft 116 100 

Forward pressure 26 39 

Fractions, to change common to decimals. . 135 75 

G 

Governor pulley, to find size of 53 57 

Grate surface per square foot of heating 

surface 91 88 

H 

Head, boiler 270-271-272-274-276 

277—278—279—280. .203—206 



OF STEAM ENGINEERS. 267 



A77. of Question. 

Head, boiler, difference between steel and 

iron 285 214 

Head, boiler, part of supported by flange. . 288 217 

Head, boiler, part of supported by tubes. . 289 218 

Head, boiler, proper thickness of flat. . . . 284 213 

Head, boiler, to reduce number of braces 

for 290 218 

Heating buildings, systems in use for. . 204-205 159 

Heating feed water, to calculate saving by 114 99 

Heating purposes, exhaust steam for 

222-223-224 175 

Heating surface of boiler 92-221 . . .88-173 

Heating surface necessary for a building. . 218 167 

Heater, feed water, with surface condenser 185 146 

Horse power, belt to transmit a given. . . . 238 184 

Horse power constant, how to find the. ... 49 54 

Horse power of an engine 43 48 

Horse power of a boiler 90 87 

Horse power, what is a 42 45 

Hyperbolic logarithms 57 61 



Indicator card, parts of an 122 104 

Indicator diagram, shows water needed for 

condenser 182 ...... 145 

Indicator, is knowledge of necessar}^ 203 157 

Indicator on compound condensing engine 177 142 

Indicator, the steam engine 119 103 

Indicating engine, precautions to be taken 202 157 

Initial cylinder condensation 153-154 133 

Initial pressure 30-178. . .40-143 

Injector, increasing capacity of 108 98 

Injector, using hot water in no 98 

Injection water 199-200-201 . . 156—157 



268 MODERN EXAMINATIONS 

No. of Question. Page. 

Irons, neutral axis of tee 295 227 

Irons, strength of tee 294 225 

jr 

Jet condenser, water necessary to run 191-192 151 

Joints 75-87 . . . .81-85 

Joint, double welt butt 76 81 

Lap, what is i 28 

Lead, what is 2 29 

Line of perfect vacuum, to locate 123 104 

Line, theoretical expansion 126 108 

Logarithms, hyperbolic 57 61 

M 

Main bearings, length of 20 37 

Main steam pipe, to determine area of 219-220. .172-173 

Mean effective pressure. 28-67-69. .39-70-71 

Mean effective pressure, to determine the 

48-55-127. .54-60-107 

Mean effective pressure, to increase 50. 54 

Mill shafting 225 178 

N 

Natural draft 116 100 

Neutral axis of tee irons 295 227 

Non-condensing engine 25 39 



Pipes, best covering for . 258 198 

Pipe, size of steam 10-219-220. . .34-172 

Pipe, size of exhaust 11 34 



OF STEAM ENGINEERS. ^69 

A'o. of Question. Page. 

Piston rod 19 37 

Pitch of rivets 72 79 

Plate, to determine strength of solid. . 73-268. . .79-201 

Plate, to determine strength of net section 74 80 

Ports, size of exhaust 13 35 

Ports, size of steam 12 35 

Power of an engine. 43-51 • • • -48-54 

Power that shafting will transmit 226-228-230 179 

Power that belts will transmit 234 183 

Pressure, bursting of boiler 266 201 

Pressure, bulging of cast iron head 274 206 

Pressure, collapsing of tubes 298 239 

Pressure, mean effective 28-67-69. .39-70-71 

Pressure, mean effective, to increase the. . 50 54 

Pressure, mean effective, to determine with- 
out the indicator 55 60 

Pressure, mean effective, to determine by 

planimeter 127 107 

Pressure, of the atmosphere 124 105 

Pressure, safe working of boiler 71 • • .74-202 

Pressure, safe working of flues 299 240 

Pressure, that flat head will carry 283 211 

Pressure, terminal 31 40 

Pulley, size of governor 53 57 

Pump, cold water 1 1 1 98 

Pump, height to which it will raise cold 

water 112 98 

Pump, to calculate contents of water cylin- 
der of 107 97 

Pump, to calculate size for a steam plant. . 106 96 

Punched holes 87 85 

Priming 98 89 

Q 

Quadruple expansion engine 39-40 41 



270 



MODERN EXAMINATIONS 



No. of Question 

Radiation, direct 209 

Radiating surface necessary for a room.. 214 

Ratio of expansion 56 

Re-evaporation 152 

Reverse an engine 5 

Rim of fly wheels 61 

Riveting, defective 251 

Rivets, pitch of 72 

Rivets, strength of 75 

Root, square 47 

Rule for distance on boiler head supported 

by flange 288 

Rule for power that a belt will transmit. . 234 

Rule for size of steam pipe 10-219-220 

Rule for work done during expansion 164-167 
Rule for water consumption 141-142 



Page. 

.163 
. 167 
. 61 
•133 

• 30 
. 64 
.T94 

• 79 
. 80 

• 50 

. 217 
.183 
34-172 
•137 
.117 



Safe load of braces 82 84 

Safe working pressure of boiler 71. . .74-202 

Safe working pressure of flues 299 ..... . 240 

Safety valve, to determine size of 100 91 

Safety valve, to determine area of opening 

101-102-103— 104-105 93 

Segment of a circle 291-292-293 220 

Separator, what is a 99 90 

Shaft, diameter of crank 14-231 . . .36-180 

Shafting, speed of 54 57 

Shafting, to determine diameter of 

225-227-229-231-232 178 

Shafting, to determine power it will trans- 
mit 226—228—230 179 

vShell, to determine thickness of 267 201 



OF STEAM ENGINEERS. 271 

JVo. of Question. Page. 

Speed of engine, to determine 45-52. . . .49-56 

Speed of fly wheels 65 68 

Spherical boiler heads, elastic limit of. . . . 276 208 

Square feet of heating surface 91-92 88 

Square root of numbers 47 50 

Stays 281-282-287 . .212-215 

Steam 133-164-165-195-222-259 

T15-137-153-175-199 

Steam engine 156 134 

Steam engine indicator 119 103 

Steam pipes, best covering for 258 198 

Steam pipes, to determine size of 10-219-220. . . .34—172 

Steam ports, to determine size of 12-13 35 

Steam plant, to determine size of pump for 106 96 

Steam plant, to determine size of chimney 

for 118 loi 

Steam space, to determine cubical contents 

of 96 89 

Steel head 272-285 204-21 1 

Strength of double welt butt joint 76 8r 

Strength of leather belting 235 183 

Strength of net section of plate 74 80 

Strength of rivets 75 80 

Strength of section of solid plate 73-268. . .79-201 

Strength of tee irons 294 225 

Super heated water 242 186 

Surface condenser 185 146 

T 

Tee irons 80—294-295 . , 85—225—227 

Temperature 1 15-186-193 . . roo-146-152 

Tensile strength of cast iron 275 207 

Terminal pressure 31-143-151—178. .40—126—133—143 

Theoretical expansion line 126 108 

Throttling engine -^2 40 

Triple expansion engine 37—38 40 

Tubes 250-289-296-297-298 . . 194-2 18-237-239 

D 

L^ncovered pipes 259. ..... 199 

Uncovered pipes, best covering for 258. 198 



272 MODERN EXAMINATIONS 

V 

A'o. of Question. Page. 

Vacuum, flow of water into a 198 155 

Vacuum, in inches, to change to pounds. . 197 ; 155 

Vacuum, line of perfect 123 104 

Valve, exhaust 145 129 

Valve, gear 60 ()2> 

Valve, globe 213 165 

Valve, how to set 4 29 

Valve rod, to determine length of 22 37 

Valve, safety 101-102-103-104-105 93 

Valve, to determine tightness of 58 62 

Volume of circulating water 183 145 

Volume of steam 133 115 

W 

Wall surface 217 168 

Water consumption from diagram 

. . . 128-129-130-131-132-137-139-141 113 

Water, cylinder of pump 107 97 

Water, flow of 198 155 

Water, heating the feed 114 99 

Water heated by exhaust steam 113 99 

Water, hot . 109-110-111 98 

Water rate, cause of high 147 131 

Water rate in compound engine 149 131 

Water required for condenser 1 82-1 91 . . 145-15 1 

Water space of boiler 93-94-95 89 

Water superheated 242 186 

Water, to test the temperature of feed .... 115 100 

Water, volume of circulating 183 145 

Wrist pin, diameter of 16 1^6 

Wrist pin, travel of 6 32 

Wrought iron boiler head 271 203 

Wrought iron shafting, to determine diam- 
eter of 225 178 

Wrought iron shafting, to determine power 

it will transmit 226 179 



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ous Tables and Examples. By John Bourne, C. E., author 
of " A Treatise on the Steam-Eng-ine," "A Treatise on the 
Screw-Propeller, " "A Cathechism of the Steam-Eng-ine, " etc. 
12mo. Cloth, $1.75. 

HAND-BOOK OF CALCnLATIO:N^S. for Engineers, Fire- 
men and Machinists. By N. Hawkins, M. E. This work is 
carefully edited, in plain lang-uag-e and everyday fig-ures. Size 
6x9 inches, weight 2>^ lbs., 336 pages, 150 illustrations ; 
strongly and handsomely bound in green silk cloth. Contains 
every calculation, rule and table necessary to be known by the 
engineer, fireman, or steam user. Price, $2.50. 

MAXIMS AND INSTRUCTIONS, for the Boiler Room. By 
N. Hawkins, M. E., deals with the following subjects: Boil- 
ers, pumps, steam heating, plumbing, piping, engineers' exam- 
inations, safety valves, valves, injectors, etc. Size 6x9 inches, 
nearly 200 illustrations, 331 pages; bound uniform with " Cal- 
culations. " Price, $2.50. 

USE AND ABUSE OF THE STEA3I BOILER, including 
its care and management. With illustrations. By Stephen 
Roper, engineer. This is the only book ever published in this 
country devoted exclusively to steam boilers. ' It contains illus- 
trations of all kinds of steam boilers now in use, whether stei- 
tionary, locomotive, fire or marine ; and also of sectional or 
patent boilers, with an elaborate description and explanation 
of the same. The safe working and bursting pressures of all 
classes of boilers ; the safe external and collapsing pressure 
of flues ; the horse-power of steam boilers ; relative proportion 
of heating to grate surface, and the strength of materials of 
which boilers are generally constructed, are fully discussed : 
nth ed. revised. 18mo, tucks, gilt edge. $2.00. 

ENGINEER'S HANDY BOOK, containing a full explana- 
tion of the steam engine indicator, and its use and advantages 
to engineers and steam users. With formulae for estimating the 
power of all classes of steam engines ; also facts, figures, 
questions and tables for engineers who wish to qualify them- 
selves for the United States Navy, the Revenue Service, the 
Mercantile Marine, or to take charge of the better class of sta- 
tionary steam engines. 14th edition, 1 vol. 16mo, 675 pages, 
tucks, gilt edge $3.50. 

THE PRACTICAU STEAM ENGINEER'S GUIDE, in the 

design, construction and management of American stationarj^ 
portable and steam fire engines, steam pumps, boilers, injec- 
tors, governors, indicators, pistons and rings, safety valves 
and steam gauges, for the use of engineers and firemen. By 
Emory Edwards. 10th edition. Illustrated by 119 engrav- 
ings. In one volume of 420 pages. Price, $2.50. 



ADVERTISEMENTS. XI 

THE AMERICAN STEAM ENGINEER. Theoretical and practi- 
cal ; with examples of the latest and most approved American 
practice, in the desigfn and construction of steam eng-ines and 
boilers of every description. For the use of eng-ineers, ma- 
chinists, boiler makers and students. By Emory Edwards, 
M. E. Illustrated by 77 engraving-s. 12mo, 419 pag-es. $2.50. 

The Engineers' Manual. Compiled by the New Haven 

stationary Eng-ineers' Association, No. 2. Containing" a vast 
amount of practical inforination which comes into daily use in 
the boiler and eng-ine room. The work treats on eng-ines and 
boilers, pumps and pumping- machinery, tog-ether with safety 
valves, injectors, steam appliances, etc., etc. Also contains 
valuable rules and tables necessary for use of eng-ineers and 
firemen. Second edition, 12mo., cloth, postpaid, 50 cents. 

A History of the Growth of the Steam Engine. By 

Robert H. Thurston, L.L. D., Director of Sibley Colleg-e, 
Cornell University, etc. With 163 illustrations. (Interna- 
tional Scientific Series). 12mo. $2.50. 

How to Run Engines and Boilers, a useful hand book 

of practical instruction for young- eng-ineers and steam users. 
By Egbert Pomeroy Watson. With a portrait of the au- 
thor. Third edition. 139 pages, fully illustrated, 16mo. , cloth. 
Price, $1.00. 

The Corliss Engine and Its Management. A practical hand 

book on the Corliss engine. By John T. Henthorn an^ C. 
D. Thurber. Synopsis of contents. Introduction and histori- 
cal, steam jacketing-, indicator cards, the g-overnor, valve g-ear 
and eccentric, valve setting-, tables for lap of steam valves, the 
air pump and its manag-ement, lubrication, care of main driv- 
ing- g-ears, heating- of mills by exhaust steam, eng-ine founda- 
tions and materials. Third edition, enlarged. 96 pages, 24 
illustrations, 16mo., cloth. Price, $1.00. 

Practical Treatise on Injectors as feeders of steam boilers, for 
the use of the master mechanic and engineers in charge of loco- 
motive, marine and stationary boilers. Contains many illus- 
trations and is a thorough and up to date treatise on the sub- 
ject. By George N. Nissenson, engineer. i2mo. , paper. 
Price, 50 cents. 

Steam Boilers. A practical treatise on boiler construction and 
examination, for the use of practical boiler makers, boiler 
users, and inspectors ; and embracing in plain figures all the 
calculations necessary in designing or classifying steam boil- 
ers. By Joshua Rose, M. E. Illustrated by 73 engravings ; 
250 pages. 8vo. Price, $2.50. 



XU ADVERTISEMENTS. 

Modern Steam Engines. An elementary treatise upon the steam 
engine, written in plain lang-uag-e ; for use in the workshop as 
well as in the drawing- office. Giving full explanations of the 
construction of modern steam engines ; including diagrams 
showing their actual operation. Together with complete but 
simple explanations of the operations of various kinds of valves, 
valve motions and link motions, etc., thereby enabling the or- 
dinary engineer to clearly understand the principles involved 
in their construction and use, and to plot out their movements 
upon the drawing board. By Joshua Rose, M. E. Illustrated 
by 422 engravings. 4to., 320 pages. Price, S6.00, 

Practical Application of the Indicator. By Lewis M. El- 
lison, C. E. A most complete and comprehensive treatise on 
indicators, with reference to the adjustment of valve gear on 
all style of engines. Written in simple language by a practi- 
cal engineer. Illustrated by 100 engravings ; 200 pages. 
Handsomely bound in cloth. Price, $2.00. 

The Steam Engine and the Indicator. Their origin and pro- 
gressive development ; including the most recent examples of 
steam and gas motors, together with the indicator, its princi- 
ples, its utility, and its application. By William Barnet Le 
Van. Illustrated by 205 engravings, chiefly of indicator 
cards ; 469 pages. 8vo. Price, $4.00. 

Indicator Practice ^^^d steam engine economy. With plain direc- 
tions for attaching the indicator, taking diag-rams, computing 
the horse power, drawing the theoretical curve, calculating 
steam consumption, determining economy, locating derange- 
ment of valves, and making all desired deductions. By Frank 
F. Hemenway, associate editor American Machinist. Price, 
$2.00. 

Slide Valve Gears. An explanation of the action and construc- 
tion of plain and cut-off slide valves. Analysis by the Bilgram 
diagram; 79 illustrations. By Frederick A. Halsey. 12mo. , 
cloth. Price, $1.50. 

Slide Valve Practically Explained. Embracing simple and 
complete practical demonstration cf the operation of each ele- 
ment in a slide valve movement, and illustrating the effects of 
variations in their proportions, by examples carefully selected 
from the most recent and successful practice. By Joshua 
Rose, M. E. ; 100 pages, 35 engravings. 12mo. , cloth. Price, 
$1.00. 

The Modern Machinist. By Johx T. Ushkr, Machinist. 
Specially adapted to the use of machinists, apprentices, de- 
signers, engineers and constructors. A practical treatise em- 
bracing the most approved methods of modern machine shop 
practice, embracing the applications of recent improved appli- 



ADVERTISEMENTS. XI 11 

ances, tools and devices for facilitating", duplicating" and expe- 
diting" the construction of machines and their parts. A new 
book from cover to cover. The author, for many years in some 
of the largest machine shops in th:s country and Eng-land, is 
fully familiar with all details of machinery. His articles, 
from time to time published in the "American Machinist," 
"Machinery'-, " etc., have been universally approved and highly 
spoken of. He hiis recently visited many of the larg-est ma- 
chine shops in this countr}^ looking" into m:iny new methods, 
which are introduced in this work. It is the latet^t, cheapest, 
and best book ever published. It cannct f^iil to be of great help 
to the master mechanic as well as to the apprentice, and the 
price puts it within the reach of all in any way interested in 
the subject. Every illustration in this book represents a new 
device in machine shop practice, and the engravings have 
been made specially for this book. 8vo. , 320 pages, 250 illus- 
trations. Price, $2.30. 

Mechanical Drawing- Self-Taug^ht. Comprising- Instructions 
in the selection and preparation of drawing" instruments, ele- 
mentary instruction in practical mechemical drawing; to- 
g-ether with examples in simple g-eometry and elementary 
mechanism, including- screw threads, g-ear wheels, mechanical 
motions, engines and boilers. By Joshua Kose, M. E. Illus- 
trated by 330 engravings, 313 pag-es 8vo. Price, $4.00. 

Haswell's Mechanics' and Engineers' Pocket 

Book. New edition ; co-ntaining much new matter, with ad- 
ditional pages. Mechanics' and Engineers' Pocket Book of 
tables, rules, and formulas pertaining to mechanics, mathe- 
matics and phj^sics, with areas, squares, cubes and roots, 
&c. ; logarithms, steam and tlie steam engine, naval architec- 
ture (including displacement of vessels, cables, chains, an- 
chor, &c., &c. ) ; masonry, steam and the steam engine, 
steam vessels, mills, &c. ; limes, mortars, cements, &c. ; or- 
thography of technicEil words and terms, &c., &c. Fifty- 
seventh edition, revised and enlarged. By Charles H. Has- 
WELL, civil, marine and mechanical engineer, member of 
American Society of Civil Engineers, and Academy of Sci- 
ences, New York ; Institutions of Civil Engineers and of 
Naval Architects, England, &c., &c. Pages 982. 12mo., 
leather, pocket book form. $4.00. 

English and American Mechanic. An every day hand book for 

the workshop and factory. Containing several thousand re- 
ceipts, rules and tables indispensable to the mechanic, the arti- 
san and the manufacturer. A new, revised, enlarged and im- 
proved edition. Edited by Emory Edwards, M. E. Frank B. 
Van Cleve. 12mo., cloth. Price, $2.00. 

American Plnnibing". By Alfred Revill. For master 
plumbers, architects, builders, apprentices, householders. A 



XIV ADVERTISEMENTS. 

compendium of practical plumbing- from solder making- to hig-h 
class open work. The only work on plumbing- containing- a 
complete drainag-e system, elevation and plan, for use of archi- 
tects and plumbers. This work tells how to make joints of all 
kinds, how to make traps, how to make bends, how to set fix- 
tures, how to provide for varying- head of water, how to run 
pipes, how to arrang-e vents, how to find defects, how to make 
repairs, how to test plumbing- work, laws and rules g-overning- 
plumbing-. Form of specifications. In short it gives in detail 
everything of importance, g-reat or small in modern plumbing ; 
225 pages devoted to the very latest improved sanitary methods 
and appliances used in plumbing; 138 illustrations, large 
12mo., cloth. Price, $2.00. 

Steam Heating for Buildings, or Hints to Steam Fitters. By 

W. J. Baldwin, being a description of steam heating appar- 
atus for warming and ventilating private houses and large 
buildings, with remarks on steam, water, and air in their rela- 
tion to heating, to which are added miscellaneous tables. Il- 
lustrated. 12mo., cloth. Price, $2.50. 

Hand Book of Land and Marine Engines, including the modeling, 

construction, rt:nning and management .of land and marine en- 
gines and boilers. With illustrations. By Stephen Roper, 
engineer. Ninth edition. 12nio. , tucks, gilt edge. Price, 
$3.^50. 

Hand Book of Modern Steam Fire Engines. With illustrations. 

By Stephen Roper, engineer. Second revised edition. 12mo. , 
tucks, gilt edge. Price, $3.50. 

Catechism of the Marine Steam Engine, for the use of engineers 

and firemen. By Emory Edwards, M. E. Illustrated by 63 
engravings, including examples of the most modern engines. 
Fifth edition, thoroughly revised, with much additional matter. 
In one volume. 12mo. , 414 pages. Price, $2.00. 

The American Marine Engineer. Theoretical and practical, 

with examples of the latest and most approved American prac- 
tice, for the use of marine engineers and students. By Emory 
Edwards. Illustrated by 85 engravings. One vol., 12mo., 440 
pages. Price, $2.50. 

Belting. A treatise on the use of belting for the transmission of 
power ; with numerous illustrations of approved and actual 
methods of arranging main driving and quarter-twist belts and 
of belt fastenings. By John H. Cooper, M. E. Third edition. 
One vol. Demy8vo. Price, $3.50. 

Electricity for Engineers. By Charles Desmond. Especially 
adapted for engineers' use. A clear and comprehensive trea- 
tise on the principles, construction and operation of dynamos, 
motors, lamps, indicators and measuring instruments ; also a 



ADVERTISEMENTS. XV 

full explanation of the electrical terms used in the work. 

Third edition. Revised and enlarg-ed. Illustrated by 130 en- 

g-raving-s. Two parts, in one volume. 12mo. , 425 pages. 
Price, $2.50. 

Theoretical and Practical Ammonia Refrigeration. A work of 

reference for eng-ineers and others employed in the manage- 
ment of ice and refrigerating machinerj". By Ityld I. Red- 
wood, Assoc. M. Am. Soc. of M. E. ; M. Soc. Chem. Indus., 
Eng. 150 pages, 15 illustrations, and 25 pages of tables. 
12 mo., cloth. $1.00. 

Catechism of the Locomotive, by Matthias N. Forney. The 
new edition is about twice the size of the original book, has cor- 
rect drawing-s of every part of the locomotive and of the different 
classes of the locomotives used in this country. It is written in 
such lang-uag-e as an eng-ineer or a fireman can easily under- 
stand, and it is believed that a study of this book will enable 
him to thoroug-hly know his business. There is no popular 
treatise in the English lang-uag-e which g-ives so clear, simple 
and complete a description of the construction and working of 
the locomotive engine. $3.50. 

Progressive Examinations of Locomotive Engineers and Fire- 
men, by John A. Hill. It contains 300 questions and answers 
to them. Seventeen colored plates showing position and color of 
every signal carried on eng-ine or train. Standard Code. 
Adopted as official examination on Railroads. Invaluable to 
engineers and firemen, and tells every young man with an am- 
bition to run a looomotive, just what he ought to know to start 
with and what he must learn before promotion. Send 50 cents 
(U. S. Stamps are good) for this neat book, pocket form, round 
covers, red and g"old. 

Hand-Book of the Locomotive, including the construction of 
Eng-ines and Boilers, and the construction, management and 
running- of locomotives. By Stephen Roper. 14th edition, re- 
vised. 18mo. , tucks, g-ilt edg-e. $2.50. 

Modern American Locomotive Engines, their design, construc- 
tion and management. A practical work for practical men. 
By Emory Edwards, M. E. Illustrated by 78 engravings. 
One volume of 383 pages, 12mo. $2.00. 

Locomotive Engine Running and Management, a treatise on 

Locomotive Engines, showing- their performance in running 
different kinds of trains with economy and despatch, etc. By 
Angus Sinclair. Illus. 12mo. $2.00. 

Air Brake Practice, '^y J- E. Phalex, of the Northern Pacific 
R, R. An exhaustive treatise on the Air Brake ; explains in 
simplest language how to operate it under all conditions. An 



XVI ADVERTISEMENTS. 

eng-ineer writes us: "The took on Air Brake Practice has 
been a source of invaluable information to me ; it is worth ten 
times the price you ask for it." Price, $1.25. 

Alexander's Ready Reference, by s. A. Alexander, for en- 

g-ineers and firemen, This book contains more valuable infor- 
mation in fewer words, and is easier understood by railroad 
men than any other book now in print, because it is written in 
the same manner that railroad men talk to each other, and by 
one who has had fort}" -two years' practical experience. It is a 
g-old mine to locomotive firemen aiming- at promotion. 
Price, $1.50. 

Modern Locomotive Construction, by j. G. A. Meyer, associate 

editor cf the " American Machinist." With many illustrations 
and fully up with the tim.es. Price, $10.00. 

Gardenier's Ready Help for Locomotive Engineers and Firemen, 

being- an educational chart for locomotive engineers and firemen 
seeking" promotion, for the scholars and students, and for the 
help of the examiner when employing- or promoting- new men, 
and is a ready help to eng-ineers while on the road. It comprises 
a remedy for every conceivable break-down or disorder that may 
occur to a locomotive, contains 600 questions and answers on 
the locomotive and air-brake. With a g-reat ainount of infor- 
mation of immense value to locomotive eng-ineers and firemen. 
Square 16mo. cloth, 117 pages. Price, $1.00. 

Hot Water Heating, Steam and Gas Fitting, by Jas. J. Lawier, 

for plumbers, steam fitters, architects, builders, apprentices, 
and householders, containing- practical information oE all the 
principles involved in the construction of Steam or Hot Water 
Plant, and how to do Gas Fitting. The illustrations show the 
latest and best appliances used for all systems. Complete plans 
for different kinds of building-s, with reg-ular working draw- 
ing's — the principles of circulation of hot water in a heating sys- 
tem illustrated and explained in the most comprehensive way. 
How to properly estimate on steam and hot water work. How 
to set up a steam and hot water plant from the foundation of the 
boiler to the bronzing of the radiators. Noises in water and 
steam pipes explained, and how to find and remedy them. The 
one and the two pipe system of steam heating illustrated. Gas 
fitting explained in all its branches, from the tapping of the 
main pipe in the street to the burners in the house. Large 12 
mo., cloth, 300 pages, elegantly illustrated. Price, postpaid, 
to any address, $2. 00. 



